Sunderland are waiting to find out the severity of Charlie Wyke's ankle ligament damage - and to discover how long the striker will be sidelined.
Wyke suffered the injury in the first half of the Black Cats' 1-0 defeat at Wycombe Wanderers, and did not re-emerge after the interval with Will Grigg coming on to replace him.
New boss Phil Parkinson said Wyke underwent a scan today but the club has not yet received the results.
"Charlie has had a scan and we're waiting for the results," said Parkinson.
"It is a blow to lose him but we have other players ready to come in and I thought Will showed a good appetite when he got on, and he has looked sharp in training again today.
" Marc McNulty is another who has looked good."
Parkinson will be forced into two changes for tomorrow night's game against Tranmere Rovers at the Stadium of Light, with Wyke's injury leaving him sidelined while Aiden McGeady will also miss out as he serves a one-match ban after collecting his fifth yellow card of the season at the weekend.
Grigg is likely to come in for Wyke, while either McNulty or Chris Maguire could come in for McGeady.
But Parkinson has also hinted that he could make more changes, conscious of the need for fresh legs with with the Tranmere game coming so rapidly after the trip to Wycombe, and also taking the opportunity to see some of the other members of his squad in action.
And that could mean George Dobson and Lynden Gooch - who were unused subs at Adams Park - could come into contention for the starting XI.
Parkinson said: "There's a quick turnaround so a bit of freshness in the team doesn't do any harm.
"There were players who did not get on the pitch on Saturday who were probably unlucky not to start the game, and there will be a chance for me to have a look at those tomorrow."
