Alexander Zverev said on Saturday that he has "several torn lateral ligaments" in his right ankle after suffering the injury during his Roland Garros semifinal against Rafael Nadal.
Order of Play| Win with SPAR | Watch Live on DStv
The German world number three turned his ankle while trailing Nadal 7-6 (10/8), 6-6 on Friday, screaming in pain before retiring from the match minutes later.
"Based on the first medical checks, it looks like I have torn several lateral ligaments in my right foot," Zverev wrote in an Instagram post.
"I will be flying to Germany on Monday to make further examinations and to determine the best and quickest way for me to recover.
"I want to thank everyone all over the world for the kind messages that I have received since yesterday."
The 25-year-old said on Friday night that he thought it was a "very serious injury".
However, if there is no fracture, he will be hopeful of returning this season.
Wimbledon gets under way in just three weeks' time, but the US Open in New York does not start until 29 August.
Zverev is still waiting for a maiden Grand Slam title, despite winning five Masters trophies and the ATP Finals twice.
Friday was his fifth major semifinal and he lost the 2020 US Open final to Dominic Thiem, having led by two sets.
Nadal, the 13-time champion, will face Norwegian Casper Ruud in Sunday's final at Roland Garros.