Second-seeded Taylor Fritz struggled with three rain delays and a stubborn Spanish opponent on Wednesday, pulling out a tight 7-5, 7-6 (7/1) win over Roberto Carballes Baena at the ATP Toronto Masters.
The second-round match was halted repeatedly by light rain, with the final 18-minute pause coming just as the second-set tiebreaker was about to start.
But Fritz, winner of Stuttgart and Eastbourne titles this season, quickly sprinted to victory before heavier rains were expected to set in.
The American was far from pleased with a win which was marred by 45 unforced errors and confessed that he has not yet felt on his game in Canada.
"Even in practice I'm having a hard time putting the ball into the court," he said. "But I'm happy to get through this one.
"Everything is not feeling great, it's tough to control the ball.
"Since I've been here it's been absolutely brutal. But I have another match to figure it out and hopefully I can play myself into the tournament."
Fritz's fourth-seeded compatriot Ben Shelton had no complaints after earning his first career win over gritty Frenchman Adrian Mannarino 6-2, 6-3.
Shelton had dropped two prior meetings with 37-year-old qualifier Mannarino but said he was able to vary his serve to get over the line this time.
"This win was huge for me. He's a shotmaker, he can take the racquet out of your hands," Shelton said. "I've played well against him in the past and come up short, he can make things really difficult."
TIAFOE HANGS ON
American Frances Tiafoe squeezed out a win after more than two and a quarter hours against Japan's Yosuke Watanuki, hailing his opponent's fighting spirit after a 1-6, 7-5, 7-6 (7/5) triumph.
"He can hit a winner on any shot," Tiafoe said. "I needed some luck in those last two sets to win."
Tiafoe managed just 19 winners to the 45 of his 158th-ranked foe, but now lines up against Australian Alexsandar Vukic, who defeated Briton Cam Norrie 6-3, 6-7 (2/7), 6-3.
Andrey Rublev, runner-up in Canada a year ago to Alexei Popyrin, won his 250th career match on hardcourt as he beat France's Hugo Gaston 6-2, 6-3.
The sixth seed needed four match points to advance after 86 minutes and now plays Italian Lorenzo Sonego, a 6-1, 6-4 winner over China's Bu Yunchaokete.
Wimbledon quarterfinalist Flavio Cobolli of Italy delivered four aces in the final game of a rain-interrupted match to clinch a 6-4, 5-7, 6-4 victory over Canadian Alexis Galarneau.
But Canadian Gabriel Diallo came out on top against his Italian opponent, beating Matteo Gigante 6-3, 7-6 (7/5) to next face Fritz.
Montreal's Felix Auger-Aliassime suffered another early disappointment, losing his opening match in his home Masters for a third straight year as he fell to Fabian Marozsan 6-4, 6-4.
Former top 10 ranking regular Stefanos Tsitsipas, now 30th in the world, continued a downward slide with a 6-4. 4-6, 6-2 loss to Australian Christopher O'Connell.
Alex de Minaur, winner in Washington on Sunday, defeated Francisco Comesana 6-4, 6-2.
"It was not pretty by any means," Australia's de Minaur said. "The wind and rain made it quite tough. I'm happy I was engaged and focused from the first point to the last.
"Backing up a good week is the toughest ask in tennis. You don't have a lot of time to enjoy the moment after a week of emotional highs.
"You have to find a way to re-set and do it all over again."
RUNE HOPES TO REAP REWARDS OF SHORT TRAINING BLOCK WITH AGASSI
World No 9 Holger Rune said his brief collaboration with Andre Agassi had given him a unique insight into how the eight-time Grand Slam champion viewed the game and hopes to use the advice he received to take his game to the next level.
Rune announced himself as one of the sport's most promising young talents three years ago by winning his first Masters title in Paris after beating four top-10 players and defeating Novak Djokovic in the final.
However, the 22-year-old has had limited success since, winning just two more titles and failing to advance beyond the quarterfinal stage at the Grand Slams.
With fellow young guns Carlos Alcaraz and Jannik Sinner now dominating the game's biggest events, Rune turned to American great Agassi earlier this month in Washington for a three-day training block.
"It was insane. I've never met a guy who sees tennis that way and I found it interesting," Rune told the Tennis Channel at the Canadian Open in Toronto.
"He makes things simple on the court. Sometimes tennis can be a difficult sport and sometimes it can be a very easy sport. There's always a reason why it's this or that.
"Some of the advice he gave me was very helpful. To share those three days, for him to get a look at my game, it was just amazing. My coach Lars (Christensen) appreciated it too, they talked a little bit and we're still in touch."
Rune said Agassi's tactics had struck a chord with him even though the Dane never watched him play growing up.
"I've watched so many YouTube clips with him on how he was taking the ball early," Rune added.
"It was so clear to see how he was making life easy for himself on the court ... it was a bit before my time so I didn't grow up watching Andre. But to look back at how tennis was then was really interesting to see."
Rune beat Giovanni Mpetshi Perricard in Toronto and next plays Alexandre Muller as he builds up for the August 24-September 7 US Open.