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 (AEST), 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

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