Drogba has consulted specialists away from Chelsea about his injury and is worried his long-term career could be affected.
He is in the treatment room at the Blues' Cobham training HQ every day but cannot see any progress being made. Grant has had heart-to-heart talks with the player because the Ivory Coast star was bitterly upset by Mourinho's departure.
But Drogba has assured him his absence is nothing to do with that or trying to engineer a move.
He told Grant: "I'm a professional and will try my best for the team and the club but I cannot play on at the moment."
Sources close to Grant insist he has an amicable relationship with Drogba and understands the player's problems.