Wayne Rooney may now be entering the career phase when he is used only in certain games for Manchester United. This was the unescapable conclusion drawn from José Mourinho’s decision to drop him to the bench and the 4-1 rout of Leicester City at Old Trafford that followed.

The victory on Saturday was significant because it reversed the rot of two successive Premier League defeats and to do so Mourinho found the ruthless streak that has been a driving part of his gilded success at Porto, Chelsea (in both spells), Internazionale and Real Madrid.

After the EFL Cup win at Northampton Town ended the run of three defeats on the bounce in all competitions – the other came in the Europa League – Mourinho examined what was needed to defeat the champions and decided his captain was surplus to requirements.

Instead Zlatan Ibrahimovic retained his place at centre-forward, and Mourinho fielded the pace of Marcus Rashford and Jesse Lingard out wide. The selection of Juan Mata at No10 was of most significance. For the first time since the Spaniard arrived in January 2014 (from Mourinho’s Chelsea) Mata was selected in his favoured position ahead of Rooney, who had to gaze on as United coasted into the break 4-0 ahead.

A 20-minute burst that featured goals from Chris Smalling, Mata, Paul Pogba (a maiden United strike) and Rashford – answered only by Demarai Gray’s second-half shot – finished the contest and may have ended Rooney’s days as a certain starter.

The Liverpudlian has been written off before – doing so is a quasi-national pastime – but Mourinho’s post-game comments may come to be viewed as the death knell for his alpha-male status in the XI. “We thought the solution for us was to play with the two fast kids and with Mata in a position where he could interact,” the Portuguese said.

The subtext here is that Mourinho decided Rooney was the inferior option to Mata to link with Lingard and Rashford. The reason is the side’s previous poor form in which Rooney’s apparent inability to stop wandering out of position clogged United’s flow.

Yet Mourinho stressed that Rooney was still his man (as the manager has to) and Smalling believes his England colleague will soon be back in the side. “I think he’s a very experienced guy and he’s played that many games that it’ll only be a matter of time before he’s back in there and firing again because he’s quality,” the defender said.

Wayne Rooney prepares to come off the bench late on during Manchester United’s win over Leicester. Photograph: Clive Brunskill/Getty Images

Mourinho talked of how Rooney was the captain not only on the field but away from it with regard to representing the club and helping out team-mates. Smalling concurred. Asked if Rooney had been down about being dropped, he said: “No. He was the same as [ever] before the game when we’re all getting ready. He is often one of the most vocal and he was the same.

“Regardless of whatever the situation is, whatever game, whether he is on the bench or playing or whatever, he is always that same type of character and that’s why he is England’s main man and our main man.”

But for how much longer? United’s next outing is the visit of Ukraine’s Zarya Lugansk on Thursday evening for the second Europa League group match. Rooney may well be recalled for a game that must be won following the defeat at Feyenoord in the opener.

This, though, may establish a pattern of the forward being deployed sparingly by Mourinho and in contests against lesser opponents. If Rooney was discarded for the challenge of Leicester what about when, say, United travel to Liverpool (the next league game but one) or are at Chelsea the following weekend?

The victory against Leicester has given Mourinho a mandate – for the foreseeable future, at least – to leave out Rooney when he wishes. A reverse to Claudio Ranieri’s side or even a less emphatic win may have provoked the question of whether Rooney is a convenient scapegoat.

Not now. For the time being the man with 246 United goals (three behind Sir Bobby Charlton’s record) may be reduced to a peripheral role.

Smalling said Rooney had been vocal in the dressing room before the match despite starting on the bench. “He had the same method,” the 26-year-old said. “Even when there’s games – obviously we play League Cup and he [Mourinho] changes the whole team, he’s still the same, in the changing room talking. That’s something that will never change with Wayne.”

The defender revealed what Mourinho’s message was beforehand. “He really wanted to get that factor over of enjoyment and enjoying it because he there’s 70-odd thousand people in the stands who would want to be in our shoes and his shoes,” he said. “It’s just a case of realising how lucky we are. And you can see that everyone did enjoy it so that message really did get across.”

How much personal satisfaction Rooney drew from not being a factor in the victory is moot. He may not have been hurdling the moon to witness the side function so well without him.

Afterwards Rooney, who came on for Rashford with seven minutes remaining, had a kickabout with his children on the pitch. The question is how soon he will again be mixing it regularly with the big boys.