The Sunderland manager didn't mind admitting before the weekend that he was looking to strengthen three key positions - left-back, centre-half and striker.

But today he revealed: "I did originally say three or four players and I'm afraid it's definitely four after the weekend.

"Martyn Waghorn suffered a knee injury in training on Sunday and looks as though he will be out for anything up to 10 weeks.

"It's a shame for the lad because he had been going well and he would have come into the squad for Saturday at Spurs.

"On top of that, we have Michael Chopra's three-game suspension kicking in next week, so you can see we are very short in that direction."

Keane's woes are compounded by the fact that last season's seven-goal top scorer Kenwyne Jones remains on the injury list and Roy O'Donovan is out on loan to Dundee United.

That leaves Daryl Murphy as the only out-and-out striker, although summer signing El-Hadji Diouf can also play up front.

The manager's words will only intensify transfer speculation surrounding the club.

Today alone the club was linked with half a dozen players.

West Ham centre-back Anton Ferdinand is believed to be edging closer to a move to Wearside, and Sunderland retain their interest in Blackburn Rovers striker Benni McCarthy – who impressed for South Africa in last night's 2-2 friendly draw with Australia at Loftus Road.

Elsewhere, Sunderland have been linked with two more strikers – Fulham's Northern Ireland hero David Healy and Sheffield United frontman James Beattie, plus three Premier League left-backs: Manchester United veteran Mikael Silvestre, Manchester City's much-travelled Michael Ball and Everton's Leighton Baines, whom Keane pursued last summer.

Sunderland have previously dismissed an interest in Beattie, and Keane said: "I'm not interested in getting into any of that.

"It's only speculation and I'm certainly not going to discuss speculation.

"We've made some good offers for players. We hope for progress very soon.

"But at this time of year there is a lot of stuff flying round which just doesn't have anything to it.

"We continue to work hard behind the scenes and as soon as anything comes off we'll let people know."