Who is Atleti's key attacking threat?

Balague, who regularly appears on BBC Radio 5 Live and La Liga TV, in addition to writing for Spain’s Sport newspaper, has observed Atletico throughout this season.

Los Colchoneros’ La Liga title defence hasn’t gone to plan, as they sit four places and 15 points adrift of league leaders and City rivals Real, with qualification for next season’s Champions League up in the air.

However, forwards Yannick Carrasco and Angel Correa have stood out for Balague, although fortunately the former is suspended for both games with United after being sent off in their final Group B encounter, with Porto.

The tricky Correa, though, is identified as someone who could cause problems for the Reds.

“I think Carrasco and Correa are the two players that when they’ve played they’ve been consistent and they have had a huge impact,” Guillem told us.

“Correa has been the best goalscorer, I think he’s scored 11 [league] goals this season, and whenever he plays, whether from the bench or starting, he creates a lot of havoc.

“He’s a little bit of an invisible striker. He appears when he’s not expected, at the second post, always running from behind to surprise the defences. If you had to pick one, it would have to be Correa.”

Matheus Cunha, signed from Hertha Berlin in the summer, has also impressed, although Balague points out that the Brazilian has been sidelined recently, meaning there is a vacancy in attack.

Antoine Griezmann is returning from a two-month lay-off, while Joao Felix is out of form, meaning it could be Luis Suarez – familiar to United fans from his spell at Liverpool – who gets the nod from manager Diego Simeone.

“Griezmann has just come back from injury and didn’t play a single minute against Osasuna [who Atletico beat 3-0 on Saturday], but Cunha is injured for two months now and he’s looked really sharp, so without him it could be a question of who leads the attack: Griezmann who’s just coming back from injury or Joao Felix, who seems a little bit fed up at the moment?

“He’s got a lot of quality as he showed with his assist to Luis Suarez at the weekend, but Simeone hasn’t made the team around him which I think is what he expected at this point.

“Luis Suarez has been struggling to score in away games in the Champions League and generally struggling to score, I think he hasn’t scored for a couple of months then he scored this weekend.

“I think he’s lost that pace he had, but in a big game where you expect to spend time in the last third, trying to find openings as a team, he has to be on the pitch.

“He generally plays these big games with Simeone.”

Despite their relatively indifferent domestic form, Atleti are not a side to be trifled with on the continental stage.

Under Simeone, they’ve reached the last eight of the Champions League on five occasions, including two finals in 2014 and 2016, losing to Real both times.

Strong home form, both at the Wanda Metropolitano and their old Vicente Calderon ground, has often been key as Atletico haven’t lost any of their 13 home knockout games in the competition with the Argentine in charge – in fact, they’ve conceded just two goals in that sequence.

So, how does Guillem feel they will approach Wednesday’s fixture, especially considering a key rule change that everyone is talking about?

“The away goal doesn’t count anymore, so a draw could be a good result. It’s a decent step into the next game, and something Simeone has always defended privately,” he replied.

“Before, when the away goal counted, a 0-0 [at home] was a good result but a draw – a 1-1, 2-2 – would be a good result, as long as it’s not a defeat which forces them to go to Old Trafford and get a result.

“How to approach it? A mixture of things. If Luis Suarez is there, it will be more difficult to pressure high so they will have to have a very solid medium block but when it comes to defending in their own box, they have to be better individually than they have been.

“They are a team that can keep the ball. It’s just that they’re not the best as an organised attack. I don’t think they have it in them to beat teams that way, so they’ll try counter-attacking too but with Luis Suarez that’s not that easy to do. He’s not the paciest.

“Correa, if he plays, or Carrasco, can certainly help. There isn’t one single way to play, both offensive or attacking.”