Lukaku began his United career with 11 goals in his first 10 games following a £75 million move from Everton in the summer, but the 24-year-old has scored just once in his last 11 appearances and missed a golden chance during the second half of the 4-2 win over Watford on Tuesday night.

Ibrahimovic returned from a seven-month layoff earlier this month and has made four substitute appearances as he works his way back to full fitness.

Former United defender Ferdinand has backed Lukaku to rediscover his goal-scoring form, but insists the Belgium international must first learn to live with the pressure of vying for a spot with Ibrahimovic.

He told BT Sport: "He'll come out of this. I think that maybe the bigger problem for him is Zlatan Ibrahimovic being there.

"Mentally, having a big striker behind you who wants to play, that's a pressure from within, and sometimes people find that hard to deal with."

Following the 1-0 win over Brighton at the weekend, Jose Mourinho said he "does not care" whether Lukaku scores or not as long as he works hard.

And despite his drought in front of goal, the United manager insists he is happy with the striker's contribution.

He said: "He works amazingly well for the team. I would never blame him for missing an easy chance, never. He's an amazing professional. I couldn't be happier with him."