Aston Villa will have to come up with in excess of £20million to persuade Sunderland to part company with striker Darren Bent.
The 26-year-old England international stunned Wearside when it emerged that he had submitted a written transfer request after the 1-1 derby draw with Newcastle.
Sunderland confirmed the move in a brief statement which said: "The club can confirm that it received a written transfer request from Darren Bent following Sunday's Wear-Tyne derby match."
However, Press Association Sport understands that the Black Cats have not yet accepted Bent's request, nor a bid of £18million from Aston Villa which reportedly could rise to as much as £24million.
Furthermore, it is understood that they would not even consider doing business for a man who cost them an initial £10million in August 2009 unless any offer significantly exceeded the £20million mark.
Manager Steve Bruce had predicted that the January transfer window would pass without major incident on Wearside, with some of the players who have spent the first half of the season out on loan possibly leaving for good while he attempted to strengthen his hand with a couple of loan signings.
He has played down speculation linking him with the likes of Adam Johnson, Charles N'Zogbia and Stewart Downing, all players in whom he has more than a passing interest - and it is understood that the Villa winger has not been offered to him as part of the bid currently on the table - while he has dismissed reports he will try to sign Michael Owen from Manchester United.
However, Bruce has been rocked by Bent's decision to submit a transfer request, and not for the first time. It is believed the former Ipswich, Charlton and Tottenham striker asked for a move during the summer, but the club managed to persuade him to stay and also keep the news under wraps.
The Black Cats were considering their options as they weighed up whether to cash in on last season's leading scorer, or to hold him to the remaining two years of his contract.
But what is certain is that, if they do decide to let him leave, they will not accept anything less than their valuation of him.