Manchester City defender John Stones' injury "does not look good", says manager Pep Guardiola.
Stones was forced off in the 43rd minute of City's 3-1 comeback win at Everton after hurting his ankle.
The England international slid in to block Everton striker Beto, who was offside but the flag had not gone up.
Asked how serious the injury was afterwards, Guardiola told Amazon Prime: "It doesn't look good, but we will see. It's his ankle."
Stones, 29, has been plagued by injuries this season. He missed the start after picking up a hip problem and was making just his eighth Premier League appearance of the campaign.