Sixth seed Jason Kubler made light work of 39-year-old Spaniard Fernando Verdasco in the first round of the Houston Open while Americans Steve Johnson and Denis Kudla advanced on Monday.

Kubler and Verdasco endured a 71-minute first-set tussle, which the Australian edged 9-7 in a tie-break before dominating the second frame, dishing out a bagel in 29 minutes to win 7-6 (9-7) 6-0.

World number 71 Kubler progressed to the second round where he will take on Colombia's Daniel Elahi Galan who defeated China's Zhang Zhizhen 6-2 6-3.

Johnson set up a second-round clash with American compatriot and top seed Frances Tiafoe after getting the better of Facundo Bagnis 7-6 (7-5) 1-6 6-1 in one hour and 55 minutes.

USA's Kudla also progressed with a hard-fought 6-4 4-6 6-4 victory over Australia's Aleksandar Vukic in just under two hours.

Dutchman Gijs Brouwer won 6-4 6-4 over Aleksandar Kovacevic, setting up a meeting with big-serving fourth seed John Isner.

Denis Shapovalov claimed a spot in the quarter-finals of the Korea Open by seeing off the challenge of Spain's Jaume Munar on Wednesday.

The 2021 Wimbledon semi-finalist needed 109 minutes to claim a 7-5 6-4 win over Munar, assuming control by breaking in the seventh game of the opener before doing likewise early in the second set.

Canadian Shapovalov – who is seeded fourth for the event – had not featured since a dramatic loss to Andrey Rublev at the US Open earlier this month, but produced a consistent display in Seoul, not committing a single double fault during the match.

His reward for the victory is a last-eight tie with Radu Albot, who held his nerve in two tie-breaks to record a 7-6 (7-3) 7-6 (7-3) win over Steve Johnson.

In Wednesday's other match, Japan's Taro Daniel beat Ecuador's Emilio Gomez in straight sets in the duo's round-of-32 tie. 

Top seed Casper Ruud begins his campaign against Nicolas Jarry on Thursday.

Dominic Thiem declared he is "definitely back" after reaching the Swedish Open quarter-finals, while Hall of Fame Open favourite Felix Auger-Aliassime crashed out in the second round. 

Thiem earned his first tour-level win in 14 months by downing Emil Ruusuvuori on his Bastad debut, before reaching his first quarter-final of the season by overcoming Roberto Bautista Agut on Thursday.

The Austrian battled to a 7-6 (7-5) 3-6 6-4 victory over the fourth-seeded Bautista Agut, picking up his first top-20 win since beating Novak Djokovic at the ATP Finals in 2020.

Sebastian Baez, who defeated Alejandro Davidovich Fokina in straight sets, awaits in the next round and former world number three Thiem is ready for the task.

"The win against Emil gave me confidence that I can compete against the best players in the world and today against Roberto," said Thiem, the 2020 US Open champion.

"He is always such a tough opponent. I was expecting and hoping it would be a close match. Then when I won the first set in the tie-break I said 'Hey, I can win today.' 

"I had the belief until the end of the match and the third set was really good. It is a process. I beat Ruusuvuori and today I beat Bautista Agut.

"Two really top opponents, so if I can beat them I am definitely back. I am into the quarters of a really strong tournament, so I am happy. It is a process, but I am going the right way."

Second seed Andrey Rublev was made to work for his 7-5 4-6 7-6 (7-2) victory over Federico Coria and will meet Laslo Djere, who defeated Marc-Andrea Huesler in straight sets to reach the quarter-finals.

Meanwhile, Auger-Aliassime resumed his match with Jason Kubler in Newport that was suspended due to bad light on Wednesday with a slight advantage but fell to a 4-6 6-3 7-6 (7-4) second-round loss.

That marked a first top-10 victory for Kubler, continuing his fine 2022 season that saw him achieve his best major result at Wimbledon, where he reached the fourth round at the All England Club.

Fourth seed Maxime Cressy is yet to drop his serve at the tournament but needed to survive a first-set scare against fellow American Steve Johnson to triumph 6-7 (3-7) 6-4 6-4.

Second favourite John Isner will meet Cressy in the semi-finals after battling past fifth seed Benjamin Bonzi 6-7 (2-7) 7-6 (8-6) 7-6 (7-5).

Taylor Fritz saw his way past Alejandro Tabilo to advance to the quarter-finals at the US Men's Clay Court Championships, winning 6-1 6-4 on Thursday.

Fresh off his maiden ATP 1000 title at Indian Wells and fourth-round run in Miami, the American world number 13 needed just 62 minutes to win in straight sets, in his first clay court match for the season.

Fritz's serve was not particularly secure, though, with the unseeded Tabilo converting on only one of six break point attempts. Fritz was more efficient and assertive when opportunities presented on the other hand, taking two of three break point chances on Tabilo's serve while winning 12 out of 19 points returning on his second serve.

Despite the Chilean world number 100 fighting back to 4-4 from 3-0 down in the second set, Fritz steadied to close out the match.

"I felt like tonight was going to be a really tough match, given he's done really well on clay," Fritz said post-match. "It was my first match [on clay]. I'm pretty happy with how I played. I can't complain, I got out of that pretty solid."

Fritz will now face another Chilean, fifth seed and defending champion Cristian Garin, who came back from a set down to defeat Jordan Thompson 3-6 6-3 6-3.

Entering the Houston event on a five-match losing streak, Garin has come from behind in back-to-back matches to win.

Sixth seed Frances Tiafoe also went the distance on Thursday, earning a 5-7 7-5 7-6 (7-4) win over Uruguayan Pablo Cuevas.

With neither garnering break point chances in the third set, Tiafoe finally created breathing room by winning four straight points at 2-2 in the deciding tie-break, before closing out the match.

It sets up an all-American quarter-final with John Isner, who defeated Steve Johnson 6-7 (1-7) 7-6 (7-4) 6-3 in Thursday's final game.

Teenage seventh seed Carlos Alcaraz fought back from a poor set to win 2-6 6-2 6-1 over fellow Spaniard Jaume Munar at the Rio Open on Monday.

The 18-year-old struggled for rhythm in the opening set but showed composure to respond by breaking Munar early in the second set and dominating from there.

Alcaraz took the victory in two hours and 15 minutes, saving 10 of 13 break points across the match, while dropping only three games in the second and third sets.

Spaniard Pedro Martinez set up a second-round clash with third seed Diego Schwartzman after a 6-3 6-4 win over Shang Juncheng.

Pablo Andujar Alba also progressed 7-6 (7-2) 7-5 over Pablo Cuevas, while Serbian qualifier Meomir Kecmanovic accounted for local wildcard Felipe Meligeni Rodrigues Alves 6-3 6-0.

At the Delray Beach Open in Florida, Steve Johnson beat South African veteran Kevin Anderson in just over two hours, triumphing 6-2 6-7 (5-7) 6-2.

Oscar Otte got past Yoshihito Nishioka 7-6 (10-8) 6-3 to set up a second-round date with top seed Cameron Norrie, while there were only two breaks across the match as seventh seed Maxime Bressy was ousted by John Millman 6-7 (2-7) 7-6 (7-2) 7-6 (7-3).

Italian veteran Andreas Seppi beat German Peter Gojowczyk 7-5 6-4, while young American Brandon Nakashima comfortably handled Denis Kudla 6-1 6-1.

Kei Nishikori is into his first ATP Tour semi-final in more than two years after defeating Lloyd Harris in straight sets at the Citi Open on Friday. 

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.

This time, Rafael Nadal could not summon the third-set magic he needed.

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. 

Top seed Milos Raonic saw his stay at the Atlanta Open come to an early end with a three-set defeat to American Brandon Nakashima on Wednesday. 

The 19-year-old Californian Nakashima, ranked 115th in the world, prevailed 5-7 6-3 7-6 (7-4) over world number 22 Raonic in their first meeting. 

The big-serving Canadian had 10 double faults to go with his 27 aces, while Nakashima did not commit one double fault and managed 13 aces. 

It was the latest in a string of recent wins over established players for Nakashima, who stunned Sam Querrey and John Isner last week at Los Cabos before falling to Cameron Norrie in the final. 

Nakashima next faces Australia's Jordan Thompson, who beat Peter Gojowczyk of Germany 7-6 (8-6) 6-4 to reach the quarter-finals. 

In the other half of the draw, fifth seed Taylor Fritz rallied to defeat fellow American Steve Johnson 6-7 (5-7) 6-4 6-1 in a rematch of a quarter-final at Los Cabos, also won by Fritz. 

Fritz will face countryman Reilly Opelka, who outlasted Bjorn Fratangelo 7-6 (7-3) 7-6 (7-4). The 6-foot-11 Opelka pounded 25 aces to just three double faults, winning 84 per cent of his service points.