Frank Sinclair believes it is clear to see that there is something wrong with Chelsea when they are playing away from home and has urged manager Maurizio Sarri to solve the problem.
Chelsea enjoyed a strong opening 45 minutes at Goodison Park on Sunday, but fell to pieces in the second half and slipped to a 2-0 loss to Everton.
The defeat has damaged the Blues' Premier League top four hopes and continues a run of poor away form since the turn of the year.
Sinclair believes there is a mental issue which is affecting the Blues and insists Sarri must sort it out soon or the side will slip further down the Premier League standings.
"There is a mental block in having the conviction to win a game away from home", Sinclair said on Chelsea TV after the game.
"That can be subconscious at times as well where you don't even realise it.
"The results don't lie. Something isn't right and the manager has touched on it in his post match interview that it is a mental thing.
"It is something he has to do something about otherwise we will slip down the league and it puts more pressure to win the Europa League."
Chelsea are through to the last eight in the Europa League and will play Slavia Prague for a spot in the semi-final.
The Blues would meet either Benfica or Eintracht Frankfurt if they can progress past the Czech outfit.
