Thibaut Courtois has thrown his future in to doubt after stalling on a contract extension, reports the Daily Mirror.
The Chelsea goalkeeper signed for the club in 2011 for £5m but has yet to make his debut for the Blues, having spent three consecutive years on loan at Atletico Madrid.
After displaying some impressive form in La Liga, Jose Mourinho was understandably keen to get Courtois tied down to a long-term deal - his current contract expires in 2016.
But Courtois has reportedly told officials at Stamford Bridge that he won't sign a new deal with the club until he gets assurance that he will be Chelsea's number one when he finally joins the west London club.
Currently Chelsea have long-standing goalkeeper Petr Cech in between the sticks and after helping Chelsea to three Premier League titles, it is hard to see anyone dislodging him.
The 21-year-old goalkeeper has grown used to being a first team regular in the Spanish league and doesn't want to move to Stamford Bridge to be understudy to Czech international Cech.
He is also aware that both Barcelona and Real Madrid are monitoring his situation and wants to be convinced that he has a future in west London before agreeing to commit to a long term deal.
Mourinho has already made it clear that he does not want to sell the Belgium international but knows his hand may be forced to do so if Courtois doesn't agree to extend his current deal.