Erik ten Hag smiles when asked if André Onana can be the “holding midfielder” for Manchester United described in Uefa’s technical report of the goalkeeper’s display for Internazionale in May’s Champions League final.

“First the job of a keeper is to save, is to [guard] his goal, that’s his main job and don’t forget this,” says United’s manager. “But, yeah, he is a keeper who we can use as an extra player and if we are developing [more] he can be more progressive and even higher up the pitch – an extra player, so that’s an advantage.”

Onana’s last game for the Italian club was the 1-0 defeat by Manchester City in Istanbul as United’s crosstown rivals claimed a first Champions League and so clinched the treble. Yet if he has recent experience of facing Pep Guardiola’s side, the 27-year-old will be a derby debutant against City in Sunday’s 191st edition of the local squabble that will attract a global audience of millions.

Uefa’s description of Onana intrigues because it suggests that what Guardiola introduced to the domestic game – a No 1 in Ederson who performs as a de facto extra defender to maintain fluidity along the backline – has evolved further. The goalkeeper was so advanced as to be a No 6 (rather than, the technical report posited, a “sweeper-keeper”) who can take up residence in the middle third of his half as his team pushes deep into enemy territory.

Onana did so against City for Internazionale but has this encounter with the champions come too soon for him to function as “the extra man” Ten Hag identifies? “It also depends on the opposition, how strong is the press, for instance, and how good is the team around him,” the United manager says.

“So if it’s possible – in my philosophy he has to do it every game [but] it is not always possible, so you have to adapt and this what I make clear. Even if you’re not playing well, if the team is not playing well, or you’re not playing to the standards you expect, you still have to win – so find a way to win, be pragmatic.”

United have been so of late, claiming victories over Sheffield United, Brentford and FC Copenhagen in their last three matches. But Ten Hag’s “depends on the opposition” and “how good is the team around him” comments sound like hints. In contrast to Inter’s Simone Inzaghi, the United manager may harbour doubts about deploying Onana high up the pitch against City.

The Dutchman is still building his team and may be wary of the uneven form of United’s new keeper. Bought for £47.2m, Onana arrived on a ticket of being a high-grade shot-stopper, technically impressive too with the ball at his feet. But until impressing against Brentford and Copenhagen, Onana had bombed, costing United goals and points.

“Certain things [here] are different,” shrugs Ten Hag when asked why the No 1 is taking time to settle in England. “OK it is 11-v-11, and it is about attacking, defending, transition. But there is more: the approach to the game, the speed of the game, the intensity. The varieties in styles. So there is absolutely a difference and players need to adjust, need time to do so.”

Last season’s derby at Old Trafford ended in a 2-1 win for United. Bruno Fernandes’s equaliser was controversial with Marcus Rashford offside but not so the goal was chalked off as he had not touched the ball. So far this term the captain has scored two goals in 12 United appearances and Ten Hag has no doubt he can be a major factor in Sunday’s showdown.

“If he does [score] again, I’ll be happy,” the manager says. “Bruno is an [effective] player when we have a lot of the ball. Then he is at his best. And there are games against top teams when you have less of the ball. So then it is about taking benefit from [any attacking] moments and for the rest you have to work hard for the team. And to get a result because that is the most important, that the team is winning.”

This is what Ten Hag has overseen in recent weeks as the protracted sale of the club has entered a new phase, with Sir Jim Ratcliffe’s bid to buy 25% for an inflated £1.3bn in return for control of football policy expected to go through imminently. But despite any implications this may have for the futures of Ten Hag’s players, the manager himself does not think the matter is a distraction.

Bruno Fernandes scores a volley for Manchester United against Burnley.

Bruno Fernandes volleys home for Manchester United against Burnley – one of two goals he has scored for the club this season. Photograph: Matthew Peters/Manchester United/Getty Images

“Of course, they are committed to the club but especially they are committed to this team,” Ten Hag says. “They want to be successful and are therefore aware you need [to focus on] the team, your teammates. That is how the players are thinking and they are not thinking about strategic reviews or structures or whatever.”

On Sunday at 3.30pm we will find out just how focused United’s players are.