Everton manager Roberto Martinez is waiting on news of striker Romelu Lukaku after he had to be substituted in their 3-0 win over Newcastle on Wednesday night.
The Belgium international got a knee in the back from Magpies defender Fabricio Coloccini just nine minutes into the match at Goodison Park and was eventually replaced at half-time.
Lukaku could not walk after the game and is now a major doubt to face Stoke in the Premier League on Saturday, with Martinez confirming he will be assessed by the club's medical staff ahead of the trip to the Britannia Stadium.
"It was a very sore one. He stayed on the pitch for a period and found it really tough to open his legs," Martinez told Sky Sports.
"He had a knee right in the middle of his back and probably had a neurological reaction and found it really difficult to be able to walk.
"We'll assess him. Obviously we've got a game around the corner against Stoke and we'll see if he can recover for that game.
"It was impossible for him to carry on."
Martinez insisted the hamstring injury which kept John Stones out of the match is not serious, though.
The England defender was a surprise omission and Everton boss Martinez revealed he had undergone a scan during the week.
Stones also missed Sunday's FA Cup win over Carlisle, but could be in contention for a return to the side for the trip to Stoke.
"John had a little bit of a niggle in his hamstring," added Martinez.
"We scanned it yesterday and it's nothing serious, but it's one of those feelings you get when you play a lot of games and a lot of minutes.
"John has had a very intense period, but I don't think he's going to be out too long. Hopefully he's going to be back next week."