SUNDERLAND made their second signing in less than a week yesterday, but Martin O’Neill has warned they cannot afford to stop there.

Centre-back Kader Mangane is on loan from Saudi Arabian club Al-Hilal until the end of the season, but the Black Cats manager stressed he is no better off in terms of squad depth. The arrival of Mangane and Alfred N’Diaye has only offset the departures.

Sunderland are still interested in Swansea City striker Danny Graham, and O’Neill hinted he might look for a specialist full-back too.

“David Meyler has left to join Hull because he wanted to play first-team football and Ji (Dong-won) has also gone (on loan to Augsburg until the end of the season),” O’Neill pointed out. “There was room in the squad anyway, but now there’s even more space to be filled.

“We’re still just two out and two in. I would still be looking to get some more people in before the end of the month. And I would certainly want more people in before we would even think about letting anyone else out.”

Like N’Diaye, Senegal international Mangane is unavailable for tonight’s FA Cup third-round replay against Bolton Wanderers, having not signed before the

original game. But when it comes to Saturday’s Premier League trip to Wigan Athletic, Mangane gives Sunderland extra options at centre-back, where their strength is greater on paper than in practice. The hunger of the 6ft 5in defender attracted O’Neill.

“He wants to try to prove himself, so we’re pleased to have him,” he said, as the final touches were being put to the deal.

“It will just add a bit of competition for places. I don’t want to be short by February 1.

“He’s a biggish lad. He knows what he’s up against and he is pretty competitive and I think he really wants to have a go.”

Mangane becomes Sunderland’s sixth senior central defender but Wes Brown has not played for just short of a year, and there is a distinct possibility he may not do so again this season after a series of knee injuries.

Titus Bramble was in the team which beat West Ham United on Saturday, but has found himself in a vicious circle this season.

Bramble needs a run of games to find his form, but without it, has struggled to get selected.

Like Matt Kilgallon, he is out of contract this summer and the chances of either player being at the Stadium of Light come July are slim.

Carlos Cuellar is injured and, while they have never kept him out for long, vice-captain John O’Shea has suffered a series of hamstring problems during his 18-month Sunderland career.

Twenty-nine-year-old Mangane – who played in Switzerland and France before signing a three-year contract in the Middle East last summer – has been handed Meyler’s old No.18 shirt.

Full-back is a more obvious concern.

Of their two specialists, Danny Rose is on a season-long loan and Phil Bardsley is another who has struggled since missing pre-season.

With Rose injured, midfielders Craig Gardner and Jack Colback filled in at the weekend, and will probably do so again tonight.

“In time, the full-back areas are definitely something we’d want to look at,” said O’Neill.

“Danny Rose has done very well and we’re hoping he will be here until the end of the season.

“But you don’t really want to be beholden to people and worrying in case something develops or someone leaves during the course of the season.

“That is something we might have a look at in the longer term.

“In an ideal world you would have a full-back going in to play full-back but it hasn’t been that way for us.”

Cash turnstiles will be in operation from 6.15pm tonight, with tickets £15 for adults.

Under-16s and over-65s can get in for £5.