Wayne Rooney has been in poor form at the start of the season, having featured regularly in the No.10 role.
Fans have called for the 30-year-old to be dropped with Paul Pogba and Henrikh Mkhitaryan potentially set to replace him.
The summer signings have so far had to accommodate themselves in the first XI in holding midfield and out wide under Mourinho.
But according to The Sun, Rooney is anxious he will lose his starting spot on Saturday at Old Trafford (12.30pm).
As a result, Mourinho is set to test Pogba and Mkhitaryan in training to see who will earn the role in attacking midfield.
The manager’s decision on whether to bench the captain is not totally made yet but the Portuguese boss is claimed to be tempted.
Juan Mata can also play as a No.10 for the Red Devils but is not expected to be ahead of the two big-name arrivals in the transfer window.
Following Rooney’s appearance as a striker at Northampton in the 3-1 EFL Cup win on Wednesday too, he did little to prove he deserves to stay in the team.
The England star hit back at critics though yesterday, saying a lot of what is said by people on his performances is “rubbish”.
Meanwhile, youngster Marcus Rashford scored again in midweek and could start on the left for United this weekend.
Jose Mourinho was unequivocal when asked what he wanted from Wayne Rooney ahead of the Northampton match in EFL Cup.
“Goals,” said Mourinho, with that familiar dead-pan delivery and death stare designed to underline the weight of his words. “Goals. I hope he scores goals.”
To say, Rooney failed to fulfil his manager’s remit is an understatement. Rooney was so wretched, so out of sorts, so shot of confidence, that Mourinho now surely has to make the biggest call of his United tenure thus far and drop his skipper for the visit of champions Leicester to Old Trafford on Saturday.
There can be no other decision if Mourinho, who has endured a frustrating and unconvincing start to his time at United, is to retain credibility in the eyes of his club’s fans and the wider football public.
The facts do not look good for Rooney and do nothing to endorse his case to be an automatic starter under Mourinho.
He has two goals in his last 18 games for United and, even though that poor return can in part be attributed to him being deployed as a deeper-lying midfielder by Van Gaal last season when he was restored by Mourinho to his favoured role as a striker on Wednesday, he was found wanting.
Rooney’s current travails are made even more glaring by the youthful zest, speed and fearlessness of his fellow striker Marcus Rashford, who did more in his second-half cameo, scoring and setting up another, than his lumbering captain did in his all too painful to watch 90-minute display.