Manchester City winger Leroy Sane damaged ankle ligaments in his side's 2-0 FA Cup fourth-round win away to Cardiff City at the weekend, the Premier League leaders confirmed on Monday.
The German was injured in a nasty challenge in the first half by Cardiff's Joe Bennett, who was shown a second yellow card for the tackle and later sent off for a second bookable offence.
Sane was replaced at half-time and City manager Pep Guardiola later said he feared he could be "out for a while", possibly a month.
While confirming the nature of the injury, City did not put a timetable on a return for Sane, who has scored 11 goals and provided 14 assists in all competitions this season.
"I suffered ankle ligament damage, but I think it isn't as bad as it looked," Sane wrote on Twitter. "My rehab will start soon and I'm motivated to be back on the pitch as soon as possible!"
Guardiola was furious about the challenge, and about a later one by Bennett on Brahim Diaz, and went onto the field after the final whistle to complain to referee Lee Mason.
Bennett was shown a second yellow for his challenge on Diaz.
Guardiola later called for referees to do more to protect players from bad challenges.
"I said many times the only thing they (referees) have to do is protect the players," he said.
"It happened once with Leroy, then it happened with Brahim again at the end.
"So for the football in general, and for the players who are the artists, they must do that. That's why we are all here."