Manchester United forward Romelu Lukaku has reportedly grown increasingly unhappy at Old Trafford in recent weeks.

Despite netting important goals against Bournemouth and West Bromwich Albion, Lukaku has failed to celebrate, which has led to questions over his behaviour.

According to The Mirror, the Belgian's actions are partly due to being used in a wide position since Zlatan Ibrahimovic's return to the first-team squad.

The Swede - who had been absent since April with a serious knee injury - has allegedly been telling his teammate to play on the flank when he has been introduced as a substitute, and boss Jose Mourinho has not moved to stop the veteran forward.

Ibrahimovic has only made one start since his return - which was marked with a goal in Wednesday's EFL Cup fixture with Bristol City - but Mourinho will be left with a decision to make should the 36-year-old continue to prove his fitness.

Lukaku has started in each of United's fixtures in the Premier League and Champions League this season, but it appears unlikely that will continue throughout the campaign.