Carlos Alcaraz won his 13th ATP match in a row as the world number one began the Toronto Masters by defeating Ben Shelton 6-3, 7-6 (7/3) on Wednesday.
The second-round battle of the two 20-year-olds went to the Spaniard, who is bidding for Canadian success after winning successive trophies at Queen's Club and Wimbledon.
Alcaraz now stands 48-4 on the season as he begins the build-up for his defence of the US Open title.
The top seed admitted that he was out-hit at times by his 41st-ranked American opponent in the 56-minute contest - his first career win in Toronto.
"He was more aggressive than me from the start," Alcaraz said. "I tried to be solid and find my rhythm but I had some trouble.
"But I'm happy to be through to the next round. Matches like this help to focus. I have to play better from now on," added Alcaraz, who faces Polish 15th seed Hubert Hurkacz in the last 16.
Elsewhere Wednesday, French veteran Gael Monfils stunned fourth seed Stefanos Tsitsipas, winning in straight sets to advance to the last 16.
The 36-year-old from Paris -- currently ranked 276th in the world -- powered past Tsitsipas 6-4, 6-3 in just under 90 minutes.
The win marked the first time Monfils has beaten a player in the top 10 since March 2022, and came against an in-form Tsitsipas fresh from winning the ATP Los Cabos title in Mexico last weekend.
Monfils, who reached the Washington third round last week, overcame 29 unforced errors to advance.
- 'Stayed cool' -
It took two match points for Monfils to get the job done, with a shotmaking duel on the first winning chance ending in Tsitsipas' favour before the French veteran closed out victory moments later.
"After (losing) the first match point, I stayed very calm and tried to make simple choices," Monfils said. "I just stayed cool, there was no panic. "I knew Stef came here with a lot of confidence and would be going for his shots.
"I played a solid match, I was very happy with the way I was moving on the court again.
"For me, it's always key to have great movement. So I was happy with that."
In other games Wednesday, second seed Daniil Medvedev advanced to the third round with a 6-2, 7-5 win over Matteo Arnaldi.
Medvedev said he needed to make more of an effort in the second set in the steamy summer conditions against Arnaldi. He struck 26 winners and 18 unforced errors.
"It felt great, but I could have played better in the second set," Medvedev said.
"There were two or three games where I had to save break points. "It was a pretty good match, now I need to improve further.
"It's hot conditions during the summer and I need to get used to them. That usually takes two or three games."
Medvedev improved to 8-1 in Toronto with his victory, his 47th this season.
Britain's Andy Murray continued to show steady improvement as the August 28 start of the US Open draws closer, with the 36-year-old defeating qualifier Max Purcell 7-6 (7/2), 3-6, 7-5.
The three-time Grand Slam champion recovered from a break down in the final set as he dug in against a feisty opponent from qualifying in a struggle lasting for nearly three hours.
Sixth seed Andrey Rublev stumbled in his first hardcourt match of the summer, losing 6-4, 6-3 to American Mackenzie McDonald.
2017 champion Alexander Zverev fell to Spaniard Alejandro Davidovich Fokina 6-1, 6-2 in 62 minutes with the German losing serve four times.
Jannik Sinner won an all-Italian battle over Matteo Berrettini 6-4, 6-3, saving all seven of the break points he faced. The seventh seed now plays Murray.
He joined countryman Lorenzo Musetti in the round of 16 after the number 19 put out Australian Thanasi Kokkinakis in a 4-6, 7-5, 6-4 fightback.
Canadian Milos Raonic, returning to the Tour after two years of injuries, continued to advance as he beat Japan's Taro Daniel 6-4, 6-3.
Young compariot Gabriel Diallo was eliminated by Australian Alex de Minaur 6-4, 7-5.
str/rcw/sev
