World number one Carlos Alcaraz overcame a foot injury scare to beat Argentina's Sebastian Baez 6-4, 6-2 on his Tokyo Open debut on Thursday, extending his sizzling run of form to reach the second round at the ATP 500 event.
The 22-year-old, who reclaimed top spot after winning the US Open earlier this month, called a medical timeout at 2-2 in the opening set after jarring his left foot while stretching for a return.
The Spaniard returned with heavy strapping but played through discomfort, breaking Baez to edge 5-4 ahead before serving out the set.
After a brief rain suspension, Alcaraz eased past Baez without facing a break to close out the contest in an hour and a half. The victory improved his season record to 63-7, having won 48 of his last 51 matches.
"I was scared. I'm not going to lie. I felt my ankle and did not feel great. I'm just happy to be able to play after that," Alcaraz said.
"I will try to be ready for the next match. It was unlucky. In the first five minutes I thought I wouldn't continue."
Alcaraz, who is aiming to become only the sixth player to win the Tokyo title while ranked world number one, will next face Belgium's Zizou Bergs.