Rooney was wasteful in possession and provided little goal threat during the 3-1 defeat to Watford and that paired with his performance in the Manchester derby against City has led to fans calling for Mourinho to change things, beginning with his captain.
Despite being only four goals away from overtaking Sir Bobby Charlton and becoming the club’s highest ever goalscorer, Rooney could be set for a spell on the sidelines, with Mourinho saying he didn’t have an issue with dropping the forward.
"I can take him out," said Mourinho after the Watford defeat. "It’s no problem for me to take him out, no problem for him to be out.”
If Mourinho does as he says he can and take out Rooney from the starting XI, it opens up a number of other options involving different personnel and formations.
4-2-3-1: De Gea, Valencia, Bailly, Smalling, Shaw, Pogba, Fellaini, Rashford, Mkhitaryan, Martial, Ibrahimovic
The first option would be a straight swap with Rooney making way for summer signing Henrikh Mkhitaryan to start in his preferred number 10 position. The Armenian has yet to play there, having made all of his United appearances on the right of a three behind Zlatan Ibrahimovic. There have been rumblings of Mkhitaryan’s frustration at not being played there and given that he scored 23 goals and assisted a further 26 he would be the natural choice to replace the England captain.
4-3-3: De Gea, Valencia, Bailly, Smalling, Shaw, Schneiderlin, Herrera, Pogba, Rashford, Ibrahimovic, Martial
Rooney’s departure from the side could result in a change of formation, with Ander Herrera coming into the side and Paul Pogba playing in a more advanced position. United have yet to get the best out of the £89m man and his best play for Juventus last term was often when he was in the final third. Morgan Schneiderlin would come in as the holding midfielder as he provides more energy than Marouane Fellaini or Michael Carrick, while Herrera’s probing forward passes would serve the lightning quick forwards Marcus Rashford and Anthony Martial. Having an extra man in midfield would also mean Rashford and Martial could play slightly closer to Ibrahimovic in a three-pronged attack.
4-4-2 (diamond): De Gea, Valencia, Bailly, Smalling, Shaw, Carrick, Herrera, Pogba, Mata, Ibrahimovic, Rashford
Despite the purchase of Pogba, United’s midfield has been overrun at times – most notably against Manchester City – so a shift to a diamond formation would help solve that problem by packing the midfield. Whilst it would mean a narrow midfield, United’s attacking full-backs Luke Shaw and Antonio Valencia would provide natural width while Rashford would be able to partner Ibrahimovic as a front two, something that worked so well for Leicester City on the way to winning the Premier League last season.
4-2-3-1: De Gea, Valencia, Bailly, Smalling, Shaw, Pogba, Herrera, Mata, Mkhitaryan, Martial, Ibrahimovic
If Mourinho is adamant on keeping the 4-2-3-1 formation that he has favoured for the majority of his career, then he could consider dropping Fellaini and playing Herrera in a deep-lying playmaker role alongside the box-to-box Pogba. Having Mata and Mkhitaryan in the side would load the side with intelligence and movement which would provide space for Pogba to run into and exploit. This tactic would mean sacrificing raw pace in favour of quick passing however.
It remains to be seen whether Rooney will survive United’s current run of poor form, but if he does find himself on the bench for a while, Mourinho is not short of options to replace him.