Costa has refused to return to Cobham this season after being told by Antonio Conte that he did not have a future at Stamford Bridge.
The Spain international was a key player for the Blues last term, scoring 24 Premier League goals, but Conte grew tired of his attitude.
Costa was keen on a return to Atletico Madrid during the summer transfer window but a move back to Spain failed to materialise.
But Conte is unwilling to hand the 28-year-old a lifeline, particularly as his replacement, Alvaro Morata, has made a superb start to his career at Chelsea.
Speaking to ITV Sport, former Republic of Ireland and United midfielder Keane…