Sunderland face competition from La Liga side Valencia for £7million Sevilla defensive midfielder Vicente Iborra.
The Black Cats lodged a bid last week, which met the asking price and has been accepted, but with interest from elsewhere the deal remains up in the air.
The Echo understands Iborra is keen on a move to Wearside to test himself in the Premier League but Valencia are also keen on the 28-year-old.
Manager David Moyes is looking to sign central midfielders, defensive cover, a goalkeeper and a striker before Wednesday night's 11pm deadline.
Iborra's agent Fede Marco told the Spanish press: "The offer from Sunderland is a market situation.
"We think it is important enough to the club and therefore the move as we have done before.
"That does not mean that Sevilla is not happy with Iborra or Iborra is not happy in Sevilla, because it is quite the opposite, but with an important offer we have to move.
"The player is what he is, a good deal. Sevilla president also has well expressed, as they have to study it and wait to see what happens."
Work is ongoing to secure Yann M'Vila's permanent return but with Russian side Rubin Kazan playing hardball over a £5million deal for a player out of contract in January, it remains complicated.
Other midfielders linked include Tottenham Hotspur's Ryan Mason and Everton's James McCarthy - with Newcastle United, Bournemouth, Crystal Palace, Watford and Celtic all interested.
Meanwhile, Sunderland are in need of another striker - and they have been linked with a shock reunion with Asamoah Gyan.
The 30-year-old spent two years on Wearside before moving to UAE club Al Ain in 2012.
Gyan - currently playing for Chinese Super League team Shanghai SIPG - looks set for a return to English football on a season-long loan.
The Ghana striker flew into the south-east of England on Sunday, with Sky Sports reporting he is set to evaluate a number of offers.
Sunderland, Fulham and several other Championship sides have been linked with a move for him.
Gyan told Sky Sports News HQ: "I have a lot of options. Me and my agent are here to evaluate them and get the work done, and then I can continue doing what I do best, which is scoring goals and playing well.
"I am confident I will have a club in England. There are good options to think about, so we had to fly in quickly. Me being in England means there is something concrete, so we need to evaluate the options and do the work.
"I heard about Sunderland and Fulham but we will see what happens. There might be surprises. Football is full of them. The people around me are trying to benefit me. It doesn't matter if it is Championship or Premier league, it's about being comfortable where I am.
"Sunderland is a good club. It was unfortunate I didn't play for many years there. I had to leave and that is football. Sometimes you stay for a long time at a club and then other times you go. I just want to prove myself again in England. I am ready to go.
"I went to the Middle East but I was scoring goals for the national team and in the world cup. I don't regret it at all and now I am back to prove myself again. Maybe it is my destiny to be back to the Premier League or the Championship.
"Maybe we will make a decision tonight, or tomorrow."