Daniil Medvedev expects to have a scan on his right ankle to see if he can continue his Indian Wells Masters campaign after injuring it in defeating Alexander Zverev.
Medvedev progressed to the quarter-finals for the first time at Indian Wells by coming from behind to defeat Zverev in three sets.
The 6-7 (5-7) 7-6 (7-5) 7-5 victory looked unlikely in the second set, when Medvedev hit the deck in obvious pain after turning his ankle.
It was subsequently taped by a physio, with Medvedev then coming through in three hours and 16 minutes, marking the longest three-set match of his career.
Medvedev has now won 17 matches in a row and is scheduled to face Alejandro Davidovich Fokina in the last eight.
But it is not yet clear whether he will be fit to play that match.
Speaking after the win over Zverev, Medvedev said: "When I twisted it, I thought I was going to stand up fine, then the pain started going fast, so I thought, 'oh no, that's not a good sign'.
"So, I honestly thought maybe one of the ligaments is a little bit injured, so I thought I'm not going to be able to play.
"That's probably one of the first times in my life where a physio taped my ankle, so I decided to give it a try, and it was very surprising. It was much easier to move and to run than to walk. When I was walking, I was limping, and then I was running fine.
"I can understand how frustrating it is for the opponent, but I was not faking it. It was tougher for me to walk.
"When the adrenaline goes down, the body cools down, it's going to be pretty painful, and I'm going to probably do a scan, see what it is and if I can continue to play."