Manchester United fear Zlatan Ibrahimovic may never be the same again after failing to make an impact upon returning from a serious knee injury.
The Swede shocked fans by returning to action in just seven months after rupturing knee ligaments in the Europa League quarter-final against Anderlecht.
But since first returning to the pitch against Newcastle last month, the 36-year-old has looked a shadow of his former self and was an unused substitute midweek against Bournemouth.
Officials at the Carrington training ground fear he will be unable to fully recover after scoring 28 times in his debut campaign at Old Trafford, report the Sun.
Mourinho is weary of pushing the veteran striker too hard and has left him out entirely of two matchday squads.
Despite Romelu Lukaku's poor run of form though, with three goals in 15 games for United, Ibrahimovic is not in a position to challenge for a starting role.
Mourinho may push for a new striker in next month's transfer window as a result in case Lukaku is unable to snap out of his bad run.