Sunderland face the prospect of having to make a cash offer for top defensive target Virgil van Dijk, rather than using Steven Fletcher in part exchange.
The Black Cats have been tracking van Dijk for the last year, with the in-demand centre-half again reiterating his desire to leave Celtic this summer in an interview in his native Holland this week.
Sunderland are expected to confirm by the weekend that Brown has agree a fresh one-year deal with the Black Cats
On the flip side of the coin, Sunderland striker Fletcher has long been a target for Celtic, ever since coming perilously close to joining the SPL champions during his time at Hibernian.
With Sunderland considering selling Fletcher this summer as he approaches the final 12 months of his contract, that has prompted speculation that a swap deal would suit all parties.
Sunderland are indeed thought to have explored that possibility, but it is understood that it would be a problematic transfer to pull off.
Sporting director Lee Congerton managed to swap flop striker Jozy Altidore for Jermain Defoe in January, but there are thought to be far more hurdles to cross in a similar deal involving Fletcher and van Dijk.
Instead, Sunderland may have to spend big if they are to beat off interest from the likes of Southampton, Everton and Arsenal for van Dijk.
Celtic have placed a £10million asking price on van Dijk’s head, despite the 24-year-old’s lack of any Premier League experience.
It is understood they would accept a smaller figure, but Sunderland still face having to pay out more than £6m.
Sunderland are in the market for two new central defenders though, even if Wes Brown has agreed a one-year contract extension to remain at the Stadium of Light.
With Sunderland also interested in re-signing last season’s loanee Sebastian Coates, Brown’s deal raises question marks over Santiago Vergini’s future.
Sunderland are duty-bound to sign Vergini after he made more than 20 appearances last season on loan, yet the £2million move could be called off if another club makes a move for the Argentine international.
However, van Dijk is clearly someone Sunderland admire after the Black Cats made an enquiry last summer and continued to scout him throughout the campaign.
And after two years at Celtic, the Dutchman has made no secret of his desire to test himself in the Premier League; believing the Scottish side cannot afford to dally over his potential sale this summer.
“Of course the Champions League millions are important for Celtic, but they cannot dismiss any interest,” he told the press in his homeland this week.
“If the correct amount is placed on the table, then they will really think about it, yes.
“If Celtic want to earn money from me, the club must act now.”