Carlos Alcaraz battled through a rain interruption to claim his 50th win of the season, defeating Jordan Thompson 7-5, 4-6, 6-3 on Wednesday at the Cincinnati Open.
The top-seeded Spaniard is bidding for his seventh trophy of 2023 as he prepares for a US Open title defence in less than a fortnight.
His victory took three hours, with the world No 1 breaking open the third set as he delivered two love games and moved through on a second match point.
"I had never played him and the start/stop was not easy," Alcaraz said. "It was not easy to wait for the rain.
"He played aggressive, I'm glad to get through. It was a long day waiting to play and then find rain in the first set.
"I had to play my best level at the end; I'm hoping for better conditions in the next round."
Alcaraz was tested by number 55 Thompson who now stands 2-16 against Top-10 opponents.
The Spaniard had 32 winners and 41 unforced errors in the marathon.
Including a 15-minute pause for rain and subsequent warmup, the first set took nearly 90 minutes, with Thompson saving 10 of a dozen break points only to lose on the first Alcaraz set point.
Alcaraz came back from a break down in the second set and ran away with the third as Thompson complained to the chair umpire about an incorrectly strung racquet which he only discovered at a late stage in the epic.
BRITISH EXODUS
In other games, an inspired Gael Monfils applied the finishing touches to a British exodus with a 3-6, 6-4, 6-3 defeat of 13th seed Cameron Norrie.
The veteran French showman got his left knee wrapped in the opening set of the first-round match and took confidence from encouraging words from the physio to secure the win which left Britain 0-3 on the day here.
The rush to the exits began with the withdrawal of Andy Murray due to an existing abdominal injury dating to last week in Toronto.
Meanwhile, on court, Lorenzo Musetti defeated Dan Evans 6-4, 6-3 before Monfils staged his comeback victory against British No 1 Norrie.
In other matches, Alexander Zverev defeated fellow former tournament champion Grigor Dimitrov 6-2, 6-2.
Germany's Zverev, the 16th seed, claimed the title at his last participation in 2021 while Dimitrov lifted the trophy in 2017.
Zverev was joined in the second round by former semifinalist Stan Wawrinka, who polished off a win after rain called a halt to his match the night before.
Switzerland's three-time Grand Slam champion defeated American Brandon Nakashima 6-3, 6-7 (5/7), 6-3, requiring just two concluding games to reach the second round after the overnight pause.
Borna Coric concluded unfinished business with Petra Korda, winning 7-6 (7/5), 6-4 while Ugo Humbert defeated fellow Frenchman Arthur Fils 6-4, 3-6, 6-2.
GARCIA OUT
In the WTA draw, the continuing career comeback of former No 1 Carolina Wozniacki failed to ignite as the Dane went down to French lucky loser Varvara Gracheva 6-4, 6-4 in 96 minutes.
Wozniacki, 33, won her first comeback match a week ago in Montreal before losing in the second round to Wimbledon winner Marketa Vondrousova.
Three-time Grand Slam runner-up Ons Jabeur, playing for the first time since losing last month's Wimbledon final, survived a struggle with Anhelina Kalinina of Ukraine to reach the third round 6-3, 6-7 (2/7), 7-6 (7/2).
Unseeded American Sloane Stephens, making her 12th tournament appearance, defeated holder Caroline Garcia 4-6, 6-4, 6-4 to reach the last 16 alongside Jabeur.
The sixth-seeded Frenchwoman had won the title here a year ago from a qualifying start, defeating three Top 10 opponents along the way.
All England Club title winner Marketa Vondrousova beat Katerina Siniakova 7-5, 6-4.
Two-time Cincinnati winner Victoria Azarenka rallied from 1-4 down in the second set to overhaul Barbora Krejcikova 6-3, 7-5.
Azarenka's fellow double Grand Slam champion Petra Kvitova took down Anna Blinkova 7-6 (7/2), 6-0.
