TONY Mowbray says Sunderland shouldn't allow Ross Stewart to leave unless they have a replacement lined up - but the striker isn't the only player the Black Cats could face a fight to keep hold of in the final hours of the transfer window.

As well as pushing to sign Stewart, Sunderland's Championship rivals Southampton are now showing an interest in Patrick Roberts.

And Sunderland have also knocked back a surprise move from Stuttgart for midfielder Pierre Ekwah.

Mowbray doesn't want to lose any of his key first team players ahead of Friday's 11pm deadline, with any departing players at this stage of the window extremely difficult to replace.

Sunderland are continuing their push to sign players, with a midfielder and a striker on the club's wishlist. But two frontmen would be needed if Stewart moves to Southampton.

Saints are expected to make a big push for the 27-year-old in the final hours of the window, with Stewart the top striker target for Russell Martin, whose side head for the Stadium of Light on Saturday.

Martin told of his admiration for Stewart - who he previously tried to sign at MK Dons - in his pre-match press conference on Wednesday, and said he hopes to sign a striker even if Southampton manage to keep Che Adams.

Stewart's Sunderland contract is due to expire at the end of the season and, despite several rounds of negotiations, the striker's representatives and the club aren't close to an agreement on a new deal.

Sunderland and most other Championship clubs can't compete with Southampton's spending power.

Mowbray understands the situation but hopes Sunderland would only sanction the exit of Stewart if they have a replacement in place.

He said: "What I would suggest is that he can't be getting sold unless the knight in shining armour comes riding through the door.

"I'd think and hope that would be the case. I'd think that we'd have a striker for the future if Ross did [leave], it's been a long time that we've been trying to get Ross to sign a new contract.

"Truthfully, I don't know what will happen with Ross. The scenario hasn't changed for me, he's either going to be here after Friday and hopefully fit in a few weeks ready to score some goals, or we take a huge bid for him and we spend all the money on strikers who are going to make the difference for us.

"That's football, the next one has to come in and score the goals and be the new hero.

"I don't know any numbers that might have been bid, if they are really good you would take the deal and spend the money? I think that's just common sense [from my perspective].

"And yet what I do know is that some of these players we look at and talk about, they are extremely overpriced and yet, isn't the whole market overpriced? I think that has trickled down from those £115 million deals in the Premier League."

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Mowbray held lengthy discussions with Sunderland owner Kyril Louis-Dreyfus and sporting director Kristjaan Speakman on Thursday afternoon, when the head coach and club chiefs discussed ins and outs.

Mowbray said: "I would like it to be busy.

"Am I expecting it to be? I think so, I hope so.

"I've just left the boardroom there with the owner in, the sporting director in, with everybody who makes the decisions in. Everyone is grafting away. So let's hope it's a busy 36 hours ahead."

Mowbray is desperate to keep Roberts at the club. The winger was last week linked with Celtic - before reports of Southampton interest emerged on Thursday - and at that stage the head said he was "100% sure" the former Manchester City forward would still be at the club after the transfer deadline.

The future of Alex Pritchard, Danny Batth and Lynden Gooch, three senior players on the fringes, remains uncertain. Mowbray has previously said he expects Pritchard to leave, while Batth looked set for Blackburn at one stage before that move broke down.

Sunderland still hope to complete the signing of Nazariy Rusyn ahead of the deadline. The Ukrainian striker revealed earlier this week that personal terms had been agreed, but Sunderland were still working to finalise a deal with his club Zorya Luhansk at that stage.