Last month's Wimbledon finalist Jabeur proved too good for American Madison Keys 7-5 6-1, winning in one hour and 22 minutes.
Jabeur, playing for the first time since Wimbledon, converted six of nine break points for the match, dominating the second set where she won 90.9 per cent first serve points.
Second seed Badosa survived a scare to win over qualifier Elizabeth Mandlik 6-2 5-7 7-6 (7-5) in two hours and 31 minutes.
Eighth seed Karolina Pliskova was knocked out by American Amanda Anisimova 3-6 7-5 6-1, while last year's runner-up Daria Kasatkina beat Taylor Townsend 6-4 6-0.
Two-time major winner Halep was forced to retire due to illness and top seed Jessica Pegula was bundled out by Daria Saville at the Citi Open.
In warm conditions, the 30-year-old Romanian battled throughout the match but eventually retired down 7-5 2-0 to Anna Kalinskaya after one hour and six minutes.
Halep had fought back from a 4-0 deficit in the first set to square it up at 5-5, before losing the first set.
However, the former world number one succumbed to illness early in the second set, handing Kalinskaya her passage into the quarter-finals.
On a dramatic day for the Citi Open favourites, world number seven Pegula was eliminated by Saville in straight sets in one hour and 38 minutes, 7-5 6-4.
Pegula was not helped by a first-serve percentage of 44.8 per cent, while she struggled to convert break points, with the Australian saving nine of 10 for the match.
Saville's win means she is 3-3 against top 20 opponents this year, progressing into the last eight where she will face Canadian qualifier Rebecca Marino.
Marino, who beat Venus Williams in her return to singles in the first round on Monday, knocked off Germany's Andrea Petkovic 6-3 3-6 6-1.
Estonian sixth seed Kaia Kanepi progressed into the quarters where she will face Kalinskaya after beating China's Zhu Lin 4-6 6-4 6-4.
The 33-year-old overcame both his high-flying opponent and a rain delay as he secured his first ATP 500 crown – and just his second Tour victory – with a 7-5 6-3 win.
The opening set stayed on serve, with Griekspoor, who was chasing his third title of the season, saving two break points in the fourth game to hold.
World number 30 Evans held to love to lead 5-4, and then had to change his racket during the next game after breaking a string.
A long return from Griekspoor then handed Evans another break chance and set point, which was saved by a booming ace from the Dutchman who then levelled things up at 5-5.
Griekspoor, who had knocked out top seed Taylor Fritz in the semi-final, then found himself 15-40 down on his next serve after a fine passing shot from Evans.
With the pressure on, a wayward return into the net from Griekspoor handed the Briton the opening set in 50 minutes.
With the second set tied at 1-1 and Evans 30-love up in the third game, play was suspended as rain began to fall. It proved, though, only a brief delay and the players did not leave the court before the match resumed.
However, Swedish umpire Mohamed Lahyani was soon again out of his chair as the drizzle continued – with Evans, leading 2-1, looking less than impressed as he sat under an umbrella for another few minutes before play was allowed to continue.
Griekspoor levelled things up on serve, but the players were forced off because of a lightning warning in the area.
Play was suspended again just before 6.30pm local time, this time looking set for a more lengthy delay and with spectators also having to leave the stadium.
The players and spectators finally returned to court more than 90 minutes later, where Evans resumed right where he left off.
He cruised through his remaining service games and dictated play on return, not facing a break point until his final game on serve.
But Evans held his nerve, saving four break point opportunities before claiming victory with a service winner.
Evans entered the event on a seven-match losing streak but won 10 straight sets en route to the title, eclipsing second seed Frances Tiafoe and fifth seed Grigor Dimitrov in the process.
It is Evans’s first ATP title since Melbourne in 2021.
The British number two eclipsed his Bulgarian opponent 6-3 7-6 (4) in just under two hours to set up a meeting with Tallon Griekspoor of the Netherlands.
Despite being overmatched in the power department, Evans put together a clean and composed performance as a sloppy Dimitrov was left to rue his own mistakes.
The world number 20 fired 24 winners to just nine from Evans, but came unstuck with 30 unforced errors.
Evans is the first British player to reach the final in Washington since Andy Murray in 2006.
Meanwhile, Griekspoor rallied from a set down in his semi-final clash with American Taylor Fritz as the world number 37 seeks his third title of the season.
The British number two arrived in the US capital on a seven-match losing streak at tour level dating back to April but, after dropping his opening set of the tournament to Gregoire Barrere, he won 10 in a row to lift the trophy.
Evans followed up victories over Frances Tiafoe and Grigor Dimitrov by defeating Dutchman Tallon Griekspoor 7-5 6-3, keeping his focus during a lengthy rain delay in the second set.
The 33-year-old hit 26 winners and only eight unforced errors and saved his only break points – four of them – in the final game.
The relief and delight on Evans’ face was evident at the end and, speaking on court, he said: “I wasn’t playing very well and I wasn’t happy with my game.
“To do the work I’ve done and to stick with it and come through is (amazing). The last game sort of summed up my week. I got out of trouble and it was an amazing week.”
It is a second ATP Tour title for Evans, who won his first in Australia at the start of 2021, and lifts him to a career high ranking of 21.
Evans had appeared at something of a loss during the grass-court season, branding his efforts against Sebastian Korda at Queen’s embarrassing and saying he was not looking forward to playing any match.
He parted ways with his Argentinian coach of two years, Sebastian Prieto, but looked full of confidence as he used his all-round skills to counter the power of Griekspoor.
One break in each set proved enough, with Evans piling on the pressure at the end of the first set and then, after rain and the threat of lightning sent players and fans from the court for more than 90 minutes at 2-2 in the second, winning the final three games of the contest.
Reflecting on his change in fortunes, Evans told reporters: “Last week I lost (against Dominik Koepfer in Atlanta), having three match points, served for the match.
“You try not to let emotions get in the way when you’re in the tournament. I was confident after the second round that I was playing well but I had to keep telling myself it was match by match and not so long ago I wasn’t playing great.
“It was really only the grass I didn’t play well. I played well in Barcelona on the clay and then I had some rough matches which I didn’t get the best out of. I lost in three (sets) a few times or tight matches.
“Then I was playing well and I just couldn’t get over the line. That’s where you lean on your team to keep you working hard and training and practising hard.
“It’s especially good to get the outcome I got this week. But I said to myself once I got into the semis that that was a good effort and then I sort of reset and wanted to win the tournament.”
Evans is a tantalising four points short of breaking the top 20 for the first time in his career but will need arguably an even better showing at the National Bank Open in Toronto this week to achieve that having reach the semi-finals of the Masters 1000 event 12 months ago.
Evans faces Canadian wild card Gabriel Diallo in the opening round and could meet British number one Cameron Norrie in round two.
The British number two eclipsed his Bulgarian opponent 6-3 7-6 (4) in just under two hours to set up a meeting with Tallon Griekspoor of the Netherlands.
Despite being overmatched in the power department, Evans put together a clean and composed performance as a sloppy Dimitrov was left to rue his own mistakes.
The world number 20 fired 24 winners to just nine from Evans, but came unstuck with 30 unforced errors.
Evans, who beat both Alexander Shevchenko and second seed Frances Tiafoe on Friday to reach the last four, is the first British player to make the final in Washington since Andy Murray in 2006.
He told the ATP’s website: “It was so hard after yesterday putting in such a big effort.
“Coming back today it was really important to not roll over and have a bad performance.
“The last few months that has happened a little bit. I’m really proud I could do that today. One more to go.”
Victory on Sunday would give Evans the second ATP title of his career following his victory in Melbourne in 2021.
Meanwhile, Griekspoor shocked American top seed Taylor Fritz in three sets in their semi-final clash as the world number 37 seeks his third title of the season.
McDonald triumphed over unseeded Japanese Nishikori 6-4 3-6 7-5 in two hours and 45 minutes in Washington DC.
The 26-year-old American's win qualifies him for his maiden ATP Tour final, sending down 4-1 aces while getting a slight edge with his return.
Nishikori, who triumphed in DC in 2015, fought back when trailing a set and a break in the second with four straight games to send it to a third.
The 31-year-old Japanese appeared to have the momentum but McDonald responded to outlast him.
McDonald will face 19-year-old Sinner who overcame another emerging talent, American 20-year-old Jenson Brooksby, 7-6 (7-2) 6-1.
Sinner becomes the first Italian to reach the final in DC and also progresses to his first ATP 500 decider.
The Italian continued his fine run in DC, having not yet dropped a set all tournament, marking a return to form after being on a four-match losing run.
Sinner saved three set points at 5-6 in the first to fight back to take the lead in a tiebreaker before a dominant second.
The world number one gave Berankis no avenues into the match, winning 48 per cent (27-of-56) of his total return points, while also converting 88 per cent (21-of-24) of his own successful first serves into points.
Medvedev will meet Serbia's Miomir Kecmanovic in the semi-final after he pulled off an impressive 6-2 6-4 victory against American Brandon Nakashima.
Kecmanovic's ability to serve his way out of trouble was the deciding factor, saving four of five break-point opportunities, while Nakashima could only save six out of 10.
Canada's Felix Auger-Aliassime booked his spot in the second semi-final after defeating America's Steve Johnson 6-4 7-6 (7-3).
The 22-year-old winner – who now sits ninth in the world rankings – served up 17 aces in the contest, while Johnson, who is usually known for his serve, could only muster four.
Cameron Norrie was a straights-sets winner over Radu Albot, although he needed a second-set tie-break to get the job done in a 6-3 7-6 (7-4) triumph.
Meanwhile, Norrie's British compatriot Daniel Evans won a war of attrition against American Taylor Fritz at the Washington Open, pulling ahead 3-6 7-6 (8-6) 4-1 before the heavy favourite retired due to the oppressive conditions.
With rising temperatures, combined with spots of rain, the humidity threatened to claim a number of scalps as multiple players in Thursday's action took extended medical timeouts, before a serious downpour halted the rest of play.
The only other matches to reach their conclusion were Yoshihito Nishioka's 7-6 (7-2) 7-6 (7-1) win against Karen Khachanov, and a 6-3 6-7 (3-7) 6-4 triumph for Sweden's Mikael Ymer against Finland's Emil Ruusuvuori.
When play resumes, Nick Kyrgios will look to finish off Reilly Opelka after reaching the rain with a 7-6 (7-1) 2-1 lead, and Grigor Dimitrov won his first set 6-4 against Sebastian Korda.
Botic van de Zandschulp was the beneficiary of the break against Frances Tiafoe, winning the first set 6-4 before slowing down in a big way to drop the second 6-2, but he will get a chance to recharge his batteries before the decider.
Coming off an epic three-hour duel Wednesday in his first match since the French Open final, Nadal fell to Lloyd Harris 6-4 1-6 6-4 on Thursday at the Citi Open.
After a short-lived maiden appearance at the Washington, D.C. tournament, the Spaniard will look ahead to Toronto and Cincinnati as he continues his preparations for the U.S. Open.
Harris, meanwhile, heads to a quarter-final matchup against veteran Kei Nishikori after recording the biggest win of his career.
Facing Nadal for the first time, the 24-year-old South African slammed 16 aces Thursday and saved four of six break points.
The 20-time grand slam winner, who battled a foot injury to outlast Jack Sock in his first match, did not have enough to answer the world number 50 on Thursday.
In addition to the top-seeded Nadal's defeat, second seed Felix Auger-Aliassime also went down Thursday, falling 6-3 6-4 to American wild card Jenson Brooksby.
With their exits, the tournament is now without its top four seeds.
That leaves fifth seed Jannik Sinner as the top player remaining after he defeated Sebastian Korda 7-6 (7-3) 7-6 (7-3).
Nishikori advanced by downing seventh seed Cameron Norrie 3-6 6-3 6-3, while John Millman knocked out eighth seed Reilly Opelka 6-3 7-6 (7-4).
Among unseeded players, Denis Kudla defeated the red-hot Brandon Nakashima 3-6 7-6 (7-3) 6-4, while Steve Johnston eased past Ricardas Berankis 6-2 6-1 and Mackenzie McDonald beat Illya Ivashka 6-4 6-4.
In addition to Harris-Nishikori, Kudla will face McDonald in the other quarter-final in the top half of the draw, while Sinner meets Johnson and Millman takes on Brooksby in the bottom half.
The 20-time Grand Slam winner needed a third-set tiebreaker to beat American wildcard Sock 6-2 4-6 7-6 (7-1).
Sock, who is currently ranked 192nd in the world, stormed back into the match with an early break in the second set after the Spaniard cruised in the first.
In a three-hour-and-a-four-minute match which saw only five breaks, Nadal got the edge winning more on his second serve, while he produced some vintage winners too.
Nadal goes through to the third round where he will face 14th seed Lloyd Harris, who progresses after a walkover with Tennys Sandgren retiring mid-match.
Third seed and world number 18 Alex De Minaur was bundled out by world number 81 Steve Johnson 6-7 (5-7) 6-4 6-2.
Fourth seed Grigor Dimitrov also was dumped out with a 6-2 7-6 (7-4) defeat to Belarussian world number 65 Ilya Ivashka.
Sixth seed Dan Evans went out in straight sets to 20-year-old American Brandon Nakashima 7-6 (7-1) 6-0 while 10th seed Taylor Fritz also bowed out to Denis Kudla 6-4 6-2.
Former winner Kei Nishikori knocked off ninth seed Alexander Bublik 6-2 7-5, while 13th seed Benoit Paire lost in three sets to Mackenzie McDonald.
Fifth seed Jannik Sinner got through in straight sets against Emil Ruusuvuori, along with eighth seed Reilly Opelka and 11th seed John Millman.
Osaka's serve was sharp and it carried her through the match, with 11 aces to Zheng's three, while giving up one break of serve and securing three breaks herself.
After Zheng fought back to win the second set, Osaka was the steady head in the decider, allowing her opponent to implode with three double-faults in crucial points to collect her first win since April.
Osaka will meet Cori Gauff in a star-studded second-round matchup after Gauff dominated Anhelina Kalinina 6-1 6-0.
She was simply too powerful for her Ukrainian opponent, winning 89 per cent (25-of-28) of her first serves to never give Kalinina a chance.
Canada's Bianca Andreescu was eliminated by American Shelby Rogers 6-4 6-2, while Russia's Veronika Kudermetova won a hard-fought battle against Italy's Camila Giorgi 7-6 (7-2) 4-6 7-5.
Meanwhile, in Washington at the Citi Open, Emma Raducanu looked in good touch as she handled the challenge of Louisa Chirico 6-4 6-2 to advance to the second round.
Raducanu will meet Colombia's Camila Osorio after she beat American Sofia Kenin 7-6 (7-2) 6-1, and top-20 talent Victoria Azarenka had no issues against Dayana Yastremska to win 6-4 6-0.
Australian Ajla Tomljanovic continued her strong run of form with a convincing 6-1 6-4 win against American Sloane Stephens, and the Czech Republic's Tereza Martincova recovered from a horrible first set to defeat Xinyu Wang 0-6 6-4 6-4.
Germany's Andrea Petkovic cruised to a 6-2 6-2 win against Denmark's Clara Tauson, and Russia's Anna Kalinskaya defeated American Madison Brengle 6-3 6-0.
In the singles, Kyrgios' serve was overpowering against his Japanese opponent, winning 76 per cent (38-of-50) of his points on serve, and saving the only break point opportunity he faced, which came early in the opening set.
His return game was also sharp, collecting breaks of serve in the first game of each set to snatch all the momentum and keep Nishioka on the back foot and chasing all day.
Kyrgios finished with 12 aces to Nishioka's three, and finished the match just like he started it with a break of serve.
It caps off a tournament where he dropped only one set in his six matches – against Frances Tiafoe in the quarter-final – to win his first singles title since this same event back in 2019.
Just a few hours later, Kyrgios was back on the court with Sock contesting the doubles final, with the pair saving both break points they faced.
After an even start, Kyrgios and Sock broke late in the first set, and then struck again to break in the opening game of the second set, going on to serve things out comfortably, never allowing Dodig and Krajicek to even reach deuce against their serve.
In doing so, Kyrgios became the first player to ever sweep both the singles and doubles in Washington.
He only had one doubles title before this season – back at the Lyon Open in 2018, also partnered with Sock – but Kyrgios has now won three in the past eight months, emerging triumphant with fellow Australian Thanasi Kokkinakis at both the Australian Open and last month's Atlanta Open.
By far the most experienced player remaining in the field after Harris' upset of Rafael Nadal on Thursday, Nishikori prevailed 6-3 7-5 to avenge a loss earlier this year in their only prior meeting.
Nishikori had lost his last six ATP quarter-final matches dating to a trip to the semis in Barcelona in April 2019.
The 31-year-old next faces Mackenzie McDonald, who downed countryman Denis Kudla 6-3 6-2 to reach his second career ATP semi-final. He has never played in a final.
In the other semi-final, fifth seed Jannik Sinner will meet wild card Jenson Brooksby.
Sinner had little trouble with American veteran Steve Johnson in a 6-4 6-2 win as the Italian won 93 per cent of his first-serve points and saved all three break points he faced.
Brooksby maintained the strong return game that as carried him all week in a 6-1 6-2 upset of 11th seed John Millman.
The Australian did not manage an ace against the 20-year-old American, who won 54 per cent of the points on Millman's serve and converted five of seven break points.
At 130 in the world, Brooksby is the lowest-seeded Citi Open semi-finalist since John Isner reached the 2007 final while ranked 416th.
Having made her breakthrough at last year's Wimbledon championships, Raducanu went on to claim a stunning success at the US Open.
The Briton defeated fellow teenager Leylah Fernandez in straight sets, becoming the first singles qualifier in the Open Era to win a grand slam title.
Yet with the North American swing fast approaching, Raducanu has not yet come close to replicating that form in 2022.
Indeed, since winning the US Open, she has reached just two WTA Tour-level quarter-finals, while she has failed to progress past the second round in any of the three majors.
While acknowledging she needs to add more consistency to her game, the 19-year-old remains relaxed, insisting she is learning to take a step back and enjoy her situation.
"My goal would be towards consistency," she told the Evening Standard. "But equally, I'm going to try and cut myself some slack.
"I'm young and I have achieved something great. I think I should step back and enjoy it.
"I'd say I am too much of a perfectionist. That drives me crazy sometimes. I obviously think it's a great trait, because I don't think I would have had the results I did without that drive and that wanting to be better.
"But it can be really self-destructive at the same time, because you're never happy and you'll always complain or find something wrong."
The Canadian-born star cites her upbringing, and the high standards set by her parents, as crucial to her success.
She added: "They've always had high standards, and told me when things weren't very good, whereas other people might have wanted to encourage me. My parents always told me how it is, and I always had this sense of wanting to prove them wrong.
"Even in primary school, we had a sprint race on sports day and for seven years straight, I won it. I'm undefeated! I really like to win. I love the fight.
"When things get tough, keep getting yourself back up. Keep persevering. Each time you do, it teaches you a lesson and you accumulate experience. Then you can grow a big bank of knowledge that you can tap into."
Raducanu is ranked 10th in the world by the WTA, and this week joined up with Dmitry Tursunov, who will coach her on a trial basis for next week's Citi Open. She split with former mentor Torben Beltz in April.
Making her first appearance since she lost in the last 16 at Wimbledon, Raducanu prevailed 6-2 3-6 6-4 over Mertens, who she also defeated at the All England Club, on Monday.
The 21-year-old elected to skip the Olympics to focus on her hard-court form and prepare for the US Open, which she won in 2021.
Raducanu's Washington campaign started with a stern test against Mertens, with the match dragging on well beyond 11pm local time.
And Raducanu conceded it was a struggle as she grappled with jet lag.
"I was playing some pretty good tennis in patches throughout, especially in the first set and moments in the third set," she said.
"I lost some focus in the second. It's not easy playing at 11:30. I got here Thursday night so I'm still jet-lagged.
"I was telling myself, 'I'm not leaving. This is not happening. You're not losing this match'.
"I've been training and playing so good in practice. I've been really on it. So on the court, I was telling myself: 'You've been so focused for so long. There's no way you're not going to try right now. You're going to fight until the very end. You didn't put all that work in for nothing'."
"I'm happy with how I pulled myself out of it, but I do need to focus."
Unseeded Russian Samsonova beat Estonian Kanepi 4-6 6-3 6-3 to take the title in Washington on Sunday.
It was Kanepi, the tournament's sixth seed, who struck first in a tight opening set with strong serving from both players, capitalising on the only break point opportunity in the 10th game.
While Samsonova won at least 70 per cent of her service points in each of the three sets, Kanepi's effectiveness dipped after the opener, with a 77 per cent (20-of-26) success rate in the first set, which dropped to 63 per cent (15-of-24) in the second and the third (12-of-19) to provide the Russian with an avenue back into the contest.
Kanepi led 3-2 in the second set, before Samsonova rattled off the next five games, securing a double break in the process and forcing a decider.
In a tight third frame, with Samsonova leading 4-3, she created three break point opportunities and only needed the first to grab a winning buffer, serving out the match for the title.
It is the 23-year-old's first singles title since her maiden victory at the German Open 14 months ago, and she only dropped two sets in the process while defeating fifth seed Elise Mertens, second seed Emma Raducanu, China's Wang Xiyu and Australia's Ajla Tomljanovic.
The Canadian world number 15 won 2-6 6-2 6-2 in just under two hours over the 37-year-old Italian.
Seppi had beaten Auger-Aliassime in the opening round at the French Open in June.
Auger-Aliassime this time hit 25 winners, including nine aces, overcoming a slow start where he was broken twice inside the opening six games to win in three sets.
Youngster Jenson Brooksby continued his bright start in Washington D.C. with a 7-6 (7-4) 7-5 win over fellow American Francis Tiafoe.
Australian Nick Kyrgios was bundled out by Mackenzie McDonald 6-4 6-4, while 12th seed Sebastian Korda eased past Vasek Pospisil 7-5 6-4 in the second round.
Seventh seed Cameron Norrie also triumphed in straight sets over Marcos Giron 6-4 6-3, while emerging star Brandon Nakashima celebrated his 20th birthday with a 6-3 6-3 victory over Alexei Popyrin.
Denis Kudla beat Feliciano Lopez to set up a second round date with 10th seed Taylor Fritz, while Tennys Sandgren will meet 14th seed Lloyd Harris after beating James Duckworth in three sets.
Finland's Emil Ruusuvuori beat India's Prajnesh Gunneswaran 2-6 6-1 6-1 and will take on fifth seed Jannik Sinner in the second round.
The sixth seed triumphed in two hours and 52 minutes, winning 7-5 4-6 7-5 over the unseeded American, who was competing in his first ATP Tour final.
The Washington, D.C. victory was 19-year-old Sinner's first ATP 500 title and his third on tour, having triumphed in Sofia late last year and Melbourne earlier this year.
Home favourite McDonald put plenty of pressure on Sinner, forcing the Italian to save seven break points for the match.
McDonald also staved off 16 break points in an enthralling contest where the Italian sent down nine aces to the American's five.
Sinner lost his serve twice in the opening set and needed 11 set points but still won 7-5, before the American hit back, dropping further behind the baseline to good effect in the second, levelling it with a 6-4 win.
The Italian claimed an early break in the last to open up a 3-0 lead, before failing to convert two championship points at 5-2.
McDonald brought it back to 5-5, with numerous dramatic rallies throughout, before the 2019 Next Gen ATP Finals champion broke in the 12th game to triumph in the third set.
Three-time grand slam winner Murray has a 19-11 win-loss record in 2022 and wants to improve that substantially before the year is out.
In March, the Scot pledged to donate the rest of his season's winnings to UNICEF's Ukraine mission, as the country endures a heavy toll of death and destruction during Russia's invasion.
A disappointing second-round loss to John Isner at Wimbledon was followed by a quarter-final exit to Alexander Bublik at the Hall of Fame Open in Newport, with those results not meeting Murray's expectations.
He is being driven by his own hunger for better results, but also an eagerness to put together a big pot of money for UNICEF's appeal.
Citi Open chairman Mark Ein announced his foundation would match Murray's winnings this week and commit that sum to the effort in Ukraine.
"You can't just forget about this," Murray said of the war. "It's still going on. People are still getting killed, children are still having to flee their homes, and are in really, really tragic situations.
"I think it's important that the media continues to shine a light on it, keep talking about it. Hopefully what the tournament is doing here can help a little bit with that.
"I just want to try and win as many matches as possible and raise as much money as I can. It will be a significant amount hopefully by the end of the year. Hopefully it makes a difference."
Stiller is a big tennis fan and has often been seen in front-row seats at the sport's top events.
He tweeted: "So much respect for @andy_murray shining a light on the millions of people - and children - still affected by this senseless war in #Ukraine."
The Reality Bites, Zoolander and There's Something About Mary actor has been a long-time Murray fan, meeting him at the 2013 US Open, a year after the British star took the Flushing Meadows title.
Murray, 35, begins his challenge at the Citi Open, staged in Washington, DC, against Sweden's Mikael Ymer on Monday.
He hailed Ein's Ukraine pledge as "brilliant", adding: "I think it really helps. It shows when the players and the tournaments work together, that really good things can happen." week.”
The decision to call off the tournament, which had been due to run from August 13 to 21 ahead of the US Open, was announced by organisers who said they were "heartbroken".
The main tennis tours have been at a standstill since March, with men's ATP and women's WTA tournaments unable to take place due to the coronavirus pandemic. Wimbledon was cancelled and the French Open has switched to a September start.
August has been inked in as the month when the tours will get back under way, and the tournament in the US capital was designated as the first ATP event after lockdown.
Several of the world's leading players had been expected to take part, aiming to pick up form and match fitness ahead of the US Open.
In a statement, Citi Open chairman Mark Ein said: "With only 23 days left until the start of the tournament, there are too many unresolved external issues, including various international travel restrictions as well as troubling health and safety trends, that have forced us to make this decision now in fairness to our players, suppliers and partners, so that they can have certainty around their planning."
Such factors could also spell trouble for the US Open, although that remains to be seen.
The United States continues to see high levels of COVID-19 positive tests, and to lose such a significant men's tour event so close to the US Open, which is due to start on August 31, is a big setback.
The ATP cited "continued uncertainties affecting the ability to meet key event planning deadlines" as being a telling factor in calling off the tournament.
It said it would continue working with the United States Tennis Association with a view to the Western and Southern Open and US Open going ahead, with both events scheduled to be played at Flushing Meadows in New York.
ATP chairman Andrea Gaudenzi said: "Unfortunately for the moment there are still large factors at play which are outside of our control. We look forward to the Citi Open returning as one of our signature American events in 2021."
Brooksby, who received a wildcard for the draw, triumphed in one hour and 49 mnutes against the former world number five.
The 20-year-old American saved a set point at 5-6 in the first set, before winning in a tiebreaker off the back of winning six consecutive points having trailed 1-4.
Former City Open finalist Anderson, who sent down 10-1 aces, had defeated Brooksby to win the Hall of Fame Open last month.
World number 130 Brooksby, who had started the season outside the top 300, claimed the crucial break in the eighth game of the second set.
Brooksby advances to take on American Francis Tiafoe, fresh from competing at Tokyo 2020, as numerous big names enter the draw for the second round.
Kei Nishikori, who won in Washington in 2015, got past American Sam Querrey 6-4 6-3 to set up a second round meeting with Kazakhstani ninth seed Alexander Bublik.
American Jack Sock will take on top seed Rafael Nadal in the second round after he got past Yoshihito Nishioka in a walkover 6-7 (3-7) 4-0.
Former top 20 player Andreas Seppi triumphed in three sets against Yasutaka Uchiyama while Canadian tour veteran Vasek Pospisil got past Emilio Gomez in three.
Ilya Ivashka, Marcos Giron, Ricardas Berankas and Daniel Galan were the other first round winners on Monday.
