LEWIS GRABBAN will miss Sunderland’s trip to Hull City tomorrow – and Black Cats boss Simon Grayson fears the striker could be out “for a number of weeks”.

Grabban injured his hamstring in Tuesday’s 1-0 defeat to Nottingham Forest, and the results of scan on the damage are due this morning.

Sunderland’s leading scorer has already been ruled out of tomorrow’s trip to the KCOM Stadium, and Grayson admits his lay-off is likely to be a relatively lengthy one.

Depending on the severity of the problem, hamstring injuries tend to a result in an absence of between three and six weeks.

Grayson said: “Lewis will miss the game through his hamstring. We're just waiting for the scan to see the severity of it. The results are coming back this morning, but he'll definitely miss the game.

“Anybody who comes off with a hamstring will be out for a period of time. It's very rare that a player will come off like that and only be out for a week or so.

“You might be talking a few weeks, but I don't know because I've not had the scan results yet. Let's hope it isn't too severe, but it's something that's probably not going to be just a few days, that's for sure.”

John O’Shea will also miss tomorrow’s game with a calf problem, but Aiden McGeady and Lamine Kone could return to the squad if they come through a full training session this morning unscathed.

Grayson said: “O'Shea will miss it (the Hull game) because he picked up a calf injury against Sheffield United which he had with Ireland previously. He's nothing long term though.

“We're waiting on McGeady and Kone to see how they are today. They haven't trained with us yet, but they have been out doing work with the physios so we're waiting to see where we go with them.”

Duncan Watmore has also been training this week, and is due to make a 45-minute appearance in tomorrow’s Under-23s game with Manchester City.

Grayson said: “He's had a good week's training and will play 45 minutes for the Under-23s tomorrow. That's a big boost for Duncan and ultimately us as a football club.

“Let's hope he comes through nicely and then we'll progress from there, but we're certainly not in a position where we're going to throw him back into the first team on Wednesday at Everton because he's been out for such a long time and we have to be very careful with that.”