Striker Darren Bent has stunned Sunderland by handing in a transfer request.
Press Association Sport understands the 26-year-old has asked to leave the club he joined for an initial 10million during the summer of 2009 amid speculation that Aston Villa have tabled an 18million bid.
The Black Cats, who have not confirmed Bent's request, are believed not to have accepted it at this stage.
Bent scored his 11th goal of the season in last weekend's 2-1 FA Cup third-round defeat by Notts County, but has managed just two in his last nine games and drew a blank in yesterday's 1-1 derby draw with Newcastle.
He enjoyed a sensational first season on Wearside after ending his nightmare at Tottenham, and rewarded manager Steve Bruce with 25 goals.
The former Ipswich and Charlton frontman missed out on a trip to last summer's World Cup finals in South Africa, the second time he had suffered the same disappointment, but scored his first senior international goal in a 3-1 Euro 2012 qualifier victory in Switzerland in September.
Bruce invested a club-record fee in excess of 13million to recruit Ghana international Asamoah Gyan to play alongside Bent in August last year, but it appears he now faces a fight to keep the pair together.