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.

Jackson double ends Man City's perfect run as Villa win
Varma leads India fightback in four-wicket victory over New Zealand
Holder Rybakina sets up Fernandez clash in Ningbo final
Bayern boss Kompany stable but sidelined for weeks, says club director
Mumbai Indians promote Pollard to head coach, replacing Jayawardene
