Events this season are not quite going as José Mourinho has told them to. There is a possibility, of course, that he was being sincere in his praise of Zlatan Ibrahimovic after the EFL Cup final and that he had no ulterior motive in telling Manchester United fans to camp at his Swedish striker’s house until he signed a new contract, but it would go so against the grain of the past 15 years of public utterances that have either been emotional outbursts or calculating manipulations that there is little point detaining ourselves any further with the notion.

So what was Mourinho attempting to achieve? In part, presumably, it was to flatter Ibrahimovic and perhaps to encourage fans to make clear to him that he is loved at Old Trafford. Equally it was probably to ensure that, if Ibrahimovic does not sign an extension to his existing deal, which expires in June, nobody can say Mourinho did not want him to stay. The possibility of Ibrahimovic leaving has become distinctly more credible this week with reports of a huge offer from LA Galaxy.

A week after Mourinho’s comments Ibrahimovic, presumably frustrated by a combination of United’s failure to finish off Bournemouth and Tyrone Mings treading on his skull, planted his elbow into the face of the defender and earned himself a three-match ban. This has been the way of Ibrahimovic and a career in which brilliance and controversy have always gone hand in hand. He scores a sensational goal one week, then lashes out, verbally or physically, the next. The elbow, clearly, took matters too far but his capacity to look after himself is part of Ibrahimovic’s greatness. He takes the ban, moves on and nobody worries too much more about it.

Except that United do need to worry about it because, as Mourinho hinted at Wembley, they have become reliant on Ibrahimovic. He has his critics at Old Trafford, those who point out that he does miss a lot of chances (particularly, seemingly, against lesser sides), but he has scored 26 goals in all competitions, with Juan Mata the next highest scorer on nine.

The statistics do, at least at first glance, seem to offer some encouragement. For all their apparent reliance on him, United’s win percentage goes up when he is not playing. Ibrahimovic has started 36 games this season of which United have won 22 (61%) and lost four (11%). They have played nine games without him in the starting line-up and won six (67%) and lost two (22%). But the encouragement soon dissipates: four of those wins without him were in the cups against lower-league sides and in one of those, at Blackburn in the fifth round of the FA Cup, it took his entry from the substitutes’ bench to turn the game United’s way.

Ibrahimovic’s influence is not just about goals. His physicality offers United an option none of his possible replacements at centre-forward can match. He has won 3.1 aerials per game this season; of those who could come in for him the next highest is Anthony Martial with 0.5. Even acknowledging that those who play wide will necessarily have fewer high balls to contest, that is a sharp drop-off. In addition there is Ibrahimovic’s aura, the charismatic authority he projects that has dragged United through certain games this season.

That said, given what happened at Stamford Bridge last time United played there, Mourinho’s approach is likely to be cautious and, if he does sit deep and play narrow as he did at Anfield, having pace in forward areas may not be such a bad thing – even if it does deny United an obvious outlet if they find themselves under pressure. That probably means no place for Wayne Rooney, who has started at centre-forward in five of the nine games Ibrahimovic has missed.

Marcus Rashford, who came in for the other four games, then becomes the most likely alternative, presumably flanked by Henrikh Mkhitaryan and Martial, with Paul Pogba pushing forward from a three-man midfield. That is if Mourinho uses the 4-2-3-1/4-3-3 hybrid he has for most of this season. Thursday’s game in Rostov, though, offered another possibility: a back three with a three-mancentre to a five-man midfield from which Pogba would break to join a front two, probably Mkhitaryan and Rashford or Martial.

The only side to beat Chelsea in the league since their switch to a back three was Tottenham, also using a back three. United probably cannot physically overpower Chelsea as Spurs did but it may be that a back three is the best way to deal with Chelsea’s two floating inside-forwards, Eden Hazard and Pedro.

Although Manchester City ended up losing 3-1, it is telling that Pep Guardiola deployed a back three against Chelsea at the Etihad in December; he, too, had reached that conclusion. And with no Ibrahimovic there is less need to get crosses into the box and so there is less need for wingers to play high up the pitch.

It may be that two different necessities come together for Mourinho. But still he would rather have Ibrahimovic available. United smashed the world transfer record last summer and yet their tactical plans may have to undergo radical revision for the absence of a 35-year-old free transfer.