Zlatan Ibrahimovic has struggled since returning for Manchester United (Picture: Getty)

Manchester United boss Jose Mourinho could sign a striker in January as fears grow over Zlatan Ibrahimovic’s ability to get back to his best after a long-term knee injury.

The Swede, 36, has defied the rules of recovery by returning after just six months after a horror knee injury in April.

The veteran has made five substitute appearances since returning for the Red Devils but he’s looked well below his best during the cameos and Mourinho’s withdrawn him from two matchday squads in order to protect him.

United fear Ibrahimovic will never hit the same heights again that saw him score 26 goals during his opening season at Old Trafford and it’s telling that Romelu Lukaku has kept his place during a dry patch where he’s scored just twice in ten games.

Ibrahimovic is yet to start for United this season (Picture: Getty)
Lukaku’s form has not seen Ibrahimovic replace him yet (Picture: Reuters)

According to the Sun, Mourinho’s considering signing a striker in January to bolster his options in the final half of what is expected to be Ibrahimovic’s final season at the club.

The Red Devils take on West Brom at the Hawthorns on Sunday and need a win to keep any type of pressure on Manchester City.

Pep Guardiola’s men have an 11-point lead at the top of the table and host Tottenham at the Etihad on Saturday evening.

MORE : Arsene Wenger wants Arsenal to secure deal for William Carvalho before World Cup begins