Sunderland are facing a huge battle to keep a clutch of their Capital One Cup heroes. Jack Colback, Phil Bardsley, Craig Gardner and Seb Larsson are all involved in contract disputes going into the final weeks of the season. All four, who played in Sunday's gallant League Cup final defeat against Manchester City, are out of contract at the end of the season, but are yet to agree extensions. Bardsley and Colback have opened talks regarding extensions, but have made it clear they are not prepared to re-sign on the terms offered. It is understood talks with Larsson and Gardner are yet to get underway, leaving the duo unsure of their futures. Sunderland's precarious top-flight status is believed to be a key factor in the north-east club's tentative approach to re-negotiating existing player contracts.