Several quarter-finals were squeezed into Saturday's schedule alongside evening semi-finals following Friday's ranout, forcing Alcaraz to play twice along with Diego Schwartzman who also progressed to Sunday's decider.
Alcaraz first defeated top seed and 2021 Wimbledon finalist Berrettini in three sets, triumphing 6-2 2-6 6-2 in two hours and two minutes.
The 18-year-old Spanish seventh seed, who reached last year's US Open quarter-finals, backed that up with a straight-sets win over Fognini, 6-2 7-5.
"It means a lot to me," Alcaraz said post-match. "I surprised myself to be able to win two matches in a row in the same day. It's tough to win one match, two is even tougher."
Third seed Schwartzman got past fellow Argentine Francisco Cerundolo 7-6 (7-4) 6-3 in a two-hour-and-two-minute semi-final, having won through earlier in the day 7-6 (7-3) 4-6 6-4 against Pablo Andujar.
The top two seeds will meet in the Delray Beach Open final in Florida after wins by Cameron Norrie and Reilly Opelka on Saturday.
First seed Norrie got past American fourth seed Tommy Paul 6-3 6-3 in one hour and 16 minutes. Norrie had endured a slow start to the calendar year, but will now play for a third ATP Tour title.
Second seed Opelka had a tougher outing, needing three hours to overcome John Millman 7-6 (10-8) 6-7 (3-7) 7-6 (7-4). In a match which only saw two breaks of serve,
Opelka, who won last week's Dallas Open title, sent down 16 aces and won 82 per cent of his first serve.
The 18-year-old became the youngest winner of an ATP 500 event since the creation of the category in 2009, clinching a 6-4 6-2 victory in one hour and 26 minutes.
Alcaraz, set to climb into the world's top 20 for the first time, captured his second tour-level title after triumphing at last year's Croatia Open.
The Spaniard won five out of six break points, including a crucial one at 4-4 on his way to taking the opening set.
Third seed Schwartzman – champion in Rio in 2018 – was appearing in his second successive final, having reached the showpiece in Buenos Aires last week.
But the Argentinian was unable to compete with the powerful seventh seed on clay, the surface on which Alcaraz could do major damage in the coming years.
Meanwhile, Cameron Norrie landed his third ATP Tour title after beating Reilly Opelka 7-6 (7-1) 7-6 (7-4) in the Delray Beach Open showpiece.
Top seed Norrie had endured a torrid start to the 2022 season, which began for him with four successive defeats.
Meanwhile, Opelka was seeking a second title in as many weeks following his triumph at the Dallas Open.
The American had won six out of six tie-breaks on his way to victory in Dallas, and a further four this week.
But despite the big-serving second seed hitting 25 aces against Norrie, taking his tournament tally to 81, and 46 winners, a total of 33 unforced errors proved costly.
Although he was denied all five opportunities to break as both sets went to a tie-break, Norrie's service game remained solid throughout and just seven unforced errors underlined his strong performance.
Alcaraz, who rose to the world number one ranking after last year's US Open triumph, won 6-2 4-6 6-2 in two hours and one minute over the Serbian in Buenos Aires.
The match marked top seed Alcaraz's first since losing to Holger Rune in the Paris Masters quarter-finals, having missed last month's Australian Open following abdominal and hamstring injuries.
The Spanish 19-year-old displayed his trademark forehand on occasion, while he was at his tenacious best, saving six of seven break points generated by Djere.
"It's a great feeling to win again," Alcaraz said post-match. "It's been a long time for me with no competition, with no matches, just recovering. Finally, I got my first win of 2023."
Alcaraz will face Serbian qualifier Dusan Lajovic next after he won 6-3 6-1 over local Camilo Ugo Carabelli.
Second seed Cameron Norrie was pushed for three hours by Argentinian wild card Facundo Diaz Acosta before prevailing 4-6 7-5 7-6 (8-6). Diaz Acosta got within two points of victory on three occasions but could not capitalise.
Norrie will face another Argentinian in the third round, with Tomas Martin Etcheverry progressing with a 4-6 6-1 6-2 win over Roberto Carballes Baena.
Third seed Denis Shapovalov was a shock second-round casualty at the Delray Beach Open after going down in here sets to Michael Mmoh on Wednesday.
The American, who is ranked 87th in the world, triumphed 7-5 3-6 6-3 in two hours and 20 minutes at the event in Florida.
The Canadian committed 30 unforced errors across the match compared to Mmoh's 16. Shapovalov also generated 10 break points but only capitalized on two, while Mmoh converted three of five.
Mmoh will take on countryman Mackenzie McDonald who won 6-3 3-6 6-2 over fifth seed Yoshihito Nishioka.
Fourth seed Miomir Kecmanovic cruised past qualifier Nuno Borges 6-3 7-5, while Marcos Giron also progressed in straight sets over Matija Pecotic.
Fritz, 25, came into the tournament sitting at a career-best rank of seventh, and he did not lose his first set in Delray Beach until the final.
The top seed, Fritz was nearly perfect in the opening set, hitting 15 winners with only one unforced error and taking 72 per cent (28-of-39) of the total points. Kecmanovic did not hit a single winner in the set.
The 23-year-old Serbian showed far more fight in the second, and after saving all three of Fritz's break-point opportunities – including one match point – Kecmanovic capitalised on his one and only break-point chance of the match to force a third set.
But the mistakes crept back into the underdog's game, shooting himself in the foot with a pair of double faults and more unforced errors than winners.
Fritz took full advantage, securing two breaks down the stretch to run away with the victory and his first title of 2023.
After winning just one of his first six finals on the ATP Tour, Fritz has now won the past four finals he has reached.
Fifth seed Garin – winner of the most recent edition in 2020 – exited a second consecutive tournament at the first-round stage after he was humbled by Federico Coria.
Coria had defeated the fifth seed, Dusan Lajovic, at last week's Argentina Open, too, but was particularly impressive on Tuesday.
A stunning 6-2 6-0 win was sealed in an hour and 16 minutes.
Coria fended off two break points midway through the first set and then won the remaining nine games in succession in a dominant victory.
Garin was the only seed to lose in Brazil, however, as Lorenzo Sonego was on the right side of a 6-2 6-0 scoreline against 2019 winner Laslo Djere.
Fabio Fognini also advanced in straight sets, while Spanish pair Albert Ramos-Vinolas and Fernando Verdasco similarly eased through.
At the Delray Beach Open, 2021 runner-up Sebastian Korda defeated Thanasi Kokkinakis in his first match since winning the Australian Open doubles title with Nick Kyrgios.
Former champion Sam Querrey came up short against Denis Istomin.
Francisco's younger brother Juan Martin had been eliminated by Hanfmann in the qualifying stage, but the fifth seed got one back on the German after leading the break point opportunities 17 to six.
Fifth-seed Cerundolo was the highest seed in action Tuesday, while sixth seed Sebastian Baez fell 3-6 7-6 (7-5) 6-3 to Serbia's Dusan Lajovic.
In the only all-Argentine clash it was Facundo Diaz Acosta prevailing 7-6 (7-5) 7-5 against Federico Coria – who sits over 100 places higher in the rankings – while Roberto Carballes Baena collected a seeded scalp with a 7-5 6-4 win over Spanish compatriot Albert Ramos-Vinolas.
Meanwhile, Australian Open quarter-finalist Ben Shelton was eliminated from his own hometown tournament as the Florida resident was bounced out of the Delray Beach Open 6-4 6-4 by Marcos Giron.
Shelton beat J.J. Wolf to reach that grand slam quarter-final, but Wolf will be moving on after he emerged with a 7-5 6-3 win against Ilya Ivashka.
Wolf will play France's Adrian Mannarino following his 4-6 6-3 6-4 triumph over Germany's Daniel Altmaier, and Mackenzie McDonald will get a shot at redemption against fifth seed Yoshihito Nishioka after a comfortable 6-2 6-2 success against Taro Daniel.
McDonald and Nishioka have played twice this year – once at the Adelaide Invitational and once at the Australian Open – and Nishioka has won all five sets.
It was also a day 33-year-old Matija Pecotic will never forget, with the world number 784 winning his first ever ATP Tour match by defeating Jack Sock 4-6 6-2 6-2.
The third seed advanced with a 6-1 6-1 victory, though that does not quite tell the whole story as the second game of the first set lasted a mammoth 24 minutes and 40 seconds.
Martinez saved eight break points in that lengthy game before finally being outdone by Schwartzman, who will now face another Spaniard in Pablo Andujar.
Incredibly, Martinez won 31 points in the first set but just one game.
"It was unbelievable," Schwartzman said. "This was probably the longest game in the history of the tournament
"I don't remember anything like this before. I played an almost perfect match, I played against an opponent that had as much confidence as me."
Andujar beat Albert Ramos-Vinolas 7-5 5-7 6-3, while fourth seed Pablo Carreno-Busta lost 5-7 6-4 6-3 to Fabio Fognini in the shock of the day.
Federico Coria awaits Fognini after following up his surprise win over defending champion Cristian Garin with a 7-6 (7-2) 4-6 6-4 victory against Fernando Verdasco.
At the Delray Beach Open, top seed Cameron Norrie beat Oscar Otte 6-3 7-5 and will face Sebastian Korda, who saw off Andreas Seppi 7-5 6-3, for a place in the semi-finals.
Tommy Paul and Stefan Kozlov are also through to the final eight in Florida after beating Denis Istomin and Steve Johnson respectively in straight sets.
Down a set when forced off on Friday, top seed Thiem failed to stave off a quarter-final loss once play resumed on Saturday.
Italian qualifier Mager turned his overnight advantage into a 7-6 (7-4) 7-5 victory before again taking to the court later in the day for his semi-final.
The 25-year-old's opponent, lucky loser Attila Balazs, earlier beat Pedro Martinez 2-6 6-4 6-2 but was left clinging onto a place in the tournament when the rain returned, the Hungarian trailing 7-6 (7-4) 3-3 against Mager.
The winner will likely face Cristian Garin in the final after the Chilean third seed opened up a 6-4 4-4 lead over Borna Coric in the other postponed semi-final.
Poor conditions also interrupted the Delray Beach Open, where Milos Raonic was unable to get underway against Reilly Opelka.
The big servers had their semi-final rescheduled for Sunday and will compete for a spot in the decider against Yoshihito Nishioka, who battled from a set down to defeat Ugo Humbert 1-6 6-4 6-0.
Nishioka has reached the final despite dropping the opener in three of his four matches at the ATP 250 event.
"After the first set I just figured out how to play against him and just kept trying to do it and then it worked," he said, as quoted by the ATP Tour.
"If I lose the first set it's okay, I just figure out how he's going to play, how I have to play against him and then from the second set I say, 'Okay, let's do it this way.'"
The former world number one had accepted a wildcard to play in the Florida event, which would have represented his first tournament of 2021.
Murray, has now pulled out of the event but the 33-year-old Scot – who has well-documented hip injuries – is not thought to have made his decision based on fitness concerns.
Instead, the ongoing global health pandemic forced Murray into a rethink over his plans with the Australian Open on the horizon.
A widely released statement from the three-time grand slam winner read: "After much deliberation with my team I've decided not to travel to play in Delray Beach.
"Given the increase in COVID-19 rates and the transatlantic flights involved, I want to minimise the risks ahead of the Australian Open.
"I'm really thankful for the understanding of the tournament and I look forward to playing there soon."
Murray has been handed a wildcard for the Australian Open, where he is a five-time finalist but has never won the tournament.
The season-open grand slam was pushed back to February 8 to allow players time a 14-day quarantine period upon arrival in Melbourne.
World number 20 Musetti is still just 20 years old, making him the third-youngest player inside the top-40. The only younger players are 19-year-olds Carlos Alcaraz (world number two) and Holger Rune (world number nine).
The talented Italian has two ATP Tour titles to his name, but none outside of Europe, and he will hope to change that after he advanced to the quarter-finals in Buenos Aires.
Musetti will play Peru's Juan Pablo Varillas next after he prevailed 6-4 6-4 against former world number three Dominic Thiem.
Fifth seed Francisco Cerundolo did his part to set up an all-Argentine quarter-final clash after dominating Jaume Munar 6-2 6-1, but compatriot Diego Schwartzman could not hold up his end of the deal, falling 6-1 6-3 to Spain's Bernabe Zapata Miralles.
Meanwhile, world number seven Taylor Fritz made a winning start to his Delray Beach Open campaign, defeating Ecuador's Emilio Gomez 6-4 6-3.
Fritz will play France's Adrian Mannarino in the quarter-final after the 34-year-old veteran eliminated 24-year-old American J.J. Wolf 7-5 6-2.
Second seed Tommy Paul was too strong for Denis Kudla in a 6-3 6-4 triumph, and he will play Radu Albot for a place in the semi-final after the Romanian emerged the 6-4 6-4 victor against Australia's Aleksandar Vukic.
Nishioka was the highest seed in action on the first day of the tournament, and he had his back up against the wall after failing to win a game in a troubling second set, but produced three breaks of serve in the back-and-forth decider.
Meanwhile, Ecuador's Emilio Gomez earned a shot at top seed and world number seven Taylor Fritz after advancing 7-6 (7-3) 6-4 against Taiwan's Tung-lin Wu.
Portugal's Nuno Borges continued his winning run after earning his spot through the qualifiers, eliminating America's Steve Johnson 6-4 3-6 6-4, but the crowd got something to cheer for when the USA's Denis Kudla got the better of Australia's Jordan Thompson 3-6 6-4 7-6 (7-2).
Further south at Argentina's Buenos Aires Open, Serbia's Laslo Djere booked a blockbuster showdown against world number two Carlos Alcaraz after repelling the challenge of Italy's Fabio Fognini 6-4 6-4.
Argentinian Pedro Cachin put on a show for his hometown fans with a 7-6 (7-2) 6-4 victory over Brazil's Thiago Monteiro, but Cachin's compatriot Guido Pella had less success with a 6-4 7-5 defeat at the hand of Spain's Jaume Munar.
Norrie eventually overcame the American fifth-seed after a final set tie-break, winning 6-2 1-6 7-6 (7-4).
The Brit's tenacity was key, saving seven of 10 break points, and he will now face another American, Tommy Paul, in the final four in Florida after he beat qualifier Stefan Kozlov 6-3 6-1.
The other semi-final will be contested between Reilly Opelka and John Millman after they bested Adrian Mannarino and Grigor Dimitrov respectively.
Opelka was taken to a third set by his French opponent before winning 7-6 (7-2) 3-6 6-1, hitting 19 aces on his way to victory.
Millan proved too good for third seed Dimitrov winning 6-4 6-4 in an hour and 34 minutes where the Australian's return was a highlight.
At the Rio Open, rain washed out many of the scheduled matches on Friday, with Diego Schwartzman against Pablo Andujar and Miomir Kecmanovic against Francisco Cerundolo both cancelled.
Matteo Berrettini and Thiago Monteiro were finally able to finish their round of 16 match at 11.35pm local time, with the Italian securing victory 6-4 6-7 (6-8) 6-3.
He will play seventh seed Carlos Alcaraz who overcame Federico Delbonis 6-4 7-6 (7-1) after their match was pushed back, starting not long prior to midnight local time.
With Saturday's play affected by rain, the big-serving American had only hours to prepare for the final after an impressive defeat of Raonic in 127 hard-hitting minutes.
Opelka edged the ace count 19 to 16 and also saved a match point against the Canadian in their semi-final, eventually coming out on top 4-6 7-6 (8-6) 6-3.
The world number 54 broke Raonic for the first time at 3-3 in the final set and then again to love to book his place in the final, where he showed no signs of tiredness when seizing the initiative by claiming the third of three set points to forge ahead against Nishioka.
However, Nishioka's return game began to click into gear and he levelled the match when Opelka sent a forehand long to lose a tense tie-break.
An immediate break put Opelka in charge of the decider, though, and he moved 5-2 up when a furious Nishioka sent a backhand wide having previously saved three break points.
Opelka secured his second ATP Tour title with a 27th ace, once again prevailing in a three-set tussle.
The Croatian came through qualifying to make his ATP Tour main-draw debut in Florida and the 33-year-old is through to the last 16 after a 4-6 6-2 6-2 victory against former world number eight Sock on Tuesday.
World number 784 Pecotic has a full-time job in finance and he will be in the money after setting up a meeting with Marcos Giron in the last 16 of the ATP 250 event.
The Princeton and Harvard graduate's boss was in his box to watch him see off Sock and Pecotic hopes he will get a chance to book a quarter-final spot on Wednesday rather than return to balancing the books.
He quipped: "I had to leave work early today. I had to send an email to the whole team. [My boss] let me off. I'm going to have to ask for another day off tomorrow."
Pecotic, who served 10 aces and struck 30 winners, added: "I certainly didn't expect to win, but certainly didn't come into the match thinking that I'm definitely going to lose.
"You've got to be realistic. This is a former top 10 guy with an incredible amount of tennis experience, with a huge serve.
"He came out serving 134 [mph] on the first serve. It would be arrogant to think that I'm going to come out and expect to win.
"But I certainly figured if I could sink my teeth into the match and work on the two or three patterns that I prepared before, that I'm going to have a chance. And then let's see... if I was going to fall under pressure or not be able to serve it out at some point. But I didn't and I got the win."
Rain wreaked havoc in Rio, where only two quarter-final matches were completed at the ATP 500 tournament on Friday.
Thiem's back is against the wall, with the Australian Open runner-up and world number four down 7-6 (7-5) 2-1 against Mager – who is featuring in his first ATP Tour quarter-final.
Lucky loser Attila Balazs and qualifier Pedro Martinez were also playing when the rain returned in Brazil, with the latter leading 6-2 2-2.
Cristian Garin managed to win through to the semi-finals after the third seed claimed his seventh successive victory by rallying past Federico Coria 2-6 6-3 7-5.
Next up for Garin is fifth seed Borna Coric, who defeated Lorenzo Sonego 7-6 (7-5) 6-3 on the Brazilian clay.
At the Delray Beach Open, second seed Milos Raonic and fellow big server Reilly Opelka will meet in the semi-finals.
Raonic beat Steve Johnson 7-6 (8-6) 6-3 and 2019 New York Open champion Opelka took down Kwon Soon-woo 6-3 6-4 at the ATP 250 event.
"It's going to be tough. He gets a lot of free points on his serve and you've got to make him play," Raonic said.
"You can't just make him play though because he goes for it from the centre of the court. You've got to move in, you've got to find a way to be aggressive."
Elsewhere, Yoshihito Nishioka overcame teenager Brandon Nakashima 3-6 7-6 (7-5) 6-4 and sixth seed Ugo Humbert eased past 2018 winner Frances Tiafoe 6-1 6-2.
Competing in his debut ATP Tour tournament, 18-year-old wildcard Nakashima defeated British qualifier Cameron Norrie 7-5 6-2 on Wednesday.
Nakashima, who is coached by 1987 Wimbledon champion and two-time Australian Open runner-up Pat Cash, is the event's youngest quarter-finalist since Kei Nishikori won the tournament as an 18-year-old in 2008.
"I always knew that I had the game to compete with these high-level pros. I just had to have the right opportunities," said Nakashima, who will face Yoshihito Nishioka after the Japanese blitzed Noah Rubin 6-1 6-2.
"I was just hoping to play a good first-round match here, but after winning these two matches, I have a lot of confidence in my game now… Hopefully I can keep it going."
Reilly Opelka – the fourth seed – dismantled Mackenzie McDonald 6-3 6-4 and Kwon Soon-woo prevailed 6-4 3-6 7-6 (7-0) against Ryan Harrison.
At the Rio Open, third seed Garin beat Federico Delbonis 6-4 6-3 en route to the quarters in Brazil.
Garin, who claimed the Cordoba Open title almost a fortnight ago, hit 22 winners to earn a meeting with Federico Coria after the Argentinian's 6-4 4-6 6-4 victory over Carlos Alcaraz.
Elsewhere, lucky loser Attila Balazs rallied past Thiago Monteiro 1-6 6-1 6-4 and Pedro Martinez trumped fellow Spaniard Pablo Andujar 6-1 6-4.
Thiem, playing his first tournament since reaching the Australian Open final, was pushed by Jaume Munar before winning 6-7 (5-7) 6-3 6-4 on the clay in Brazil.
The Austrian top seed, who won the ATP 500 event in 2017, needed two hours, 41 minutes to advance, having also dropped a set in his opener.
Thiem will face Gianluca Mager in the quarter-finals after the Italian qualifier's 6-3 7-6 (7-5) victory over Joao Domingues.
Borna Coric moved into the last eight courtesy of a 6-3 1-6 7-6 (7-5) win against wildcard Thiago Seyboth Wild.
The fifth seed will meet Lorenzo Sonego, who upset second seed Dusan Lajovic 7-6 (7-5) 7-6 (7-5).
At the Delray Beach Open, Raonic – the 2017 runner-up – served 11 aces in a 7-5 6-3 win over Cedrik-Marcel Stebe that sent him into the quarter-finals.
Steve Johnson awaits the Canadian after overcoming 2017 champion Jack Sock 6-4 5-7 6-1.
Frances Tiafoe, the 2018 winner, and Ugo Humbert set up a last-eight meeting with straight-sets victories over Tommy Paul and Miomir Kecmanovic respectively.
Thiem, last in action in an Australian Open final loss to Novak Djokovic, returned with a 6-2 4-6 6-1 victory over wildcard Felipe Meligeni Alves on Tuesday.
The 2017 champion of the ATP 500 event played on clay in Brazil, top seed Thiem grabbed two breaks of serve in the deciding set.
Having started 2020 with four losses in five matches, Borna Coric found a victory by overcoming Juan Ignacio Londero 7-6 (7-5) 7-5.
Dusan Lajovic joined Thiem and Coric as the three seeds to win, but two fell in the opening round.
Casper Ruud, coming off a title win at the Argentina Open, went down to qualifier Gianluca Mager 7-6 (7-4) 7-5.
Guido Pella, the 2016 runner-up, was edged by Thiago Monteiro 5-7 6-4 7-6 (7-3) after just over three hours.
At the Delray Beach Open, Sock claimed his first non-Laver Cup singles win since late 2018.
The American 2017 champion, a wildcard, battled past last year's winner Radu Albot 3-6 6-3 7-6 (7-2), saving a match point in the final set and breaking down in tears following his victory.
Canadian second seed Milos Raonic brushed past lucky loser Denis Istomin 6-2 6-2 and Reilly Opelka served 20 aces in a 6-7 (5-7) 6-4 7-6 (7-4) victory over Ernests Gulbis.
Ugo Humbert, the French sixth seed, battled through, while third seed Taylor Fritz fell to qualifier Cameron Norrie 6-4 6-7 (4-7) 6-4.
With Norrie having already set up a quarter-final against last year's runner-up Sebastian Korda, the Briton was joined in the last eight by the second and third seeds.
Grigor Dimitrov defeated Mitchell Krueger to mark his first appearance since a disappointing second-round exit at the Australian Open in style.
The Bulgarian won 7-6 (7-4) 6-3, with Serena and Venus Williams watching on from the crowd in far from ideal conditions in Florida.
"It's always very tough [in your opening match], especially playing the last match on," Dimitrov said.
"I've been here for a week already and I was eager to get out there and play. Today was just a match I had to get through. Very tough conditions: rain, wind, cold, hot. It is what it is, and you've got to deal with it."
Opelka, who won the tournament in 2020, went the distance against fellow American Jack Sock, eventually prevailing 6-7 (6-8) 7-6 (7-4) 6-1.
He will face Adrian Mannarino in the last eight, after the Frenchman's 6-4 2-6 7-5 defeat of Brandon Nakashima. Dimitrov will play Australian John Millman.
At the Rio Open, only two of the four scheduled matches were completed due to rain.
Qualifier Miomir Kecmanovic dispatched sixth seed Lorenzo Sonego 7-5 6-4, while Francisco Cerundolo overcame Roberto Carballes Baena.
Top seed Matteo Berrettini's clash with Brazilian Thiago Monteiro was pushed back to Friday, while Carlos Alcaraz will resume his match against Federico Delbonis in a strong position in the first set.
Verdasco, the ninth seed at the ATP 500 tournament, was beaten 6-3 6-3 by fellow Spaniard Pablo Andujar on the clay in Brazil.
The 36-year-old has fallen to three straight losses, the first of which was a third-round defeat at the Australian Open.
Verdasco – the 2018 runner-up – was one of three seeds tested, but Garin survived a test against Andrej Martin.
Garin, who won the title in Cordoba earlier this month, needed more than three hours to edge Martin 4-6 7-5 7-6 (7-5).
Albert Ramos-Vinolas departed, the seventh seed falling to 16-year-old Carlos Alcaraz 7-6 (7-2) 4-6 7-6 (7-2) after three hours, 36 minutes.
Federico Delbonis advanced, while wildcard Thiago Seyboth Wild needed almost four hours to get past Alejandro Davidovich Fokina 5-7 7-6 (7-3) 7-5.
There were also upsets at the Delray Beach Open, where John Millman and Adrian Mannarino were beaten in the first round.
Millman, the fifth seed, went down to Yoshihito Nishioka 3-6 6-4 6-2 and seventh seed Mannarino fell to Kwon Soon-woo 1-6 6-3 6-2.
Frances Tiafoe, the champion in 2018, came through his opener against qualifier Emilio Gomez.
