Rio Ferdinand believes Zlatan Ibrahimovic's return could be behind Romelu Lukaku's recent goal drought.

The Manchester United striker failed to score for the 10th time in 11 games as his side won 4-2 at Watford on Tuesday night (28 November), squandering a glorious chance to put his side four goals up before the hosts threatened to mount a comeback.

The 24-year-old hit the ground running after moving to Old Trafford from Everton for an initial fee of £75m, scoring 10 goals over his first nine appearances across the Premier League and the Champions League.

However, the goals have since dried up, with Lukaku having gone four league games without a goal before he found the back of the net against Newcastle United on 18 November.

The game against the Magpies marked Zlatan Ibrahimovic's return to action, as the Swede made his debut this season following seven months out after rupturing his knee ligaments in April. While Ibrahimovic's return has bolstered Jose Mourinho's options up-front, Ferdinand believes it has also had a negative impact on Lukaku's form.

"He'll come out of this," the former United defender said on BT Sport after the game against Watford. "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."

Mourinho, however, insisted he was happy with the Belgian's contribution. The Portuguese coach had defended his striker after he failed to score against Brighton and Hove Albion over the weekend and reiterated he was pleased with the former Everton man, who laid on Anthony Martial's goal.

"Lukaku needs a big contract with a new boots company," the United manager joked. "They need to pay him lots of money so that he can start scoring again. He is such an amazing player for the team, such a good professional. He works so hard."

Tuesday's win at Vicarage Road was the first time United have picked three points on the road since they beat Southampton in September and allowed the 20-time champions of England to momentarily close the gap to Manchester City to five points.

The assignments for Mourinho's men will get even trickier over the next 10 days, as United face Arsenal at The Emirates on Saturday [2 December], a ground where they have lost their last two visits without scoring a goal, before hosting City on 10 December.

The trip to north London could be a pivotal moment in United's season, particularly given Mourinho's dismal record away from home against the so-called Big Six. Since Mourinho took charge of United, they have picked up three points out of a possible 21 when facing the likes of Arsenal, Spurs, Chelsea,Liverpool and City on the road, scoring just once.