One of Europe's more fiery bosses - he is no stranger to a red card - Simeone's expressive touchline antics regularly spark as much conversation as his success as a manager.

As the ex-Argentina midfielder prepares to mastermind his club's route into the Champions League quarter-finals with the tie against Manchester United locked at 1-1, former Atletico defender Kieran Trippier told BBC Radio 5 Live what it is like to play for Simeone.

Tripper was signed by him for £20m in 2019 and went on to win the La Liga title before moving to Newcastle in January.

'He's phoned me when I'm asleep'

Kieran Trippier: I was very excited to go and play for him, and what you see on the touchline, this is what he is like every day in training. He is so emotional, obsessed.

There have been times when I've been in bed, asleep, and he has called me. It is crazy, something I have never experienced. He is talking about things I could have done better and I'm trying to sleep.

I've had random texts, calls from him talking about the game and that is where he is obsessed. He is an unbelievable manager. Emotional is the exact word to describe him.

Every moment he is football crazy. His documentary shows how he is on a daily basis. He is an incredible manager and I am just fortunate to have worked with him because I have learnt so much from him.

'You need to run through a brick wall for him'

Kieran Trippier: The training was relentless, it was crazy. He is one of those managers where you need to run through a brick wall for him.

If you don't work hard he will just pull you out. He doesn't care how good or how big a name you are - you need to run.

In training, even in the warm-ups with the passing drills, if it is not the right quality he will let you know. He is exactly the same as he is on the touchline.

He is relentless, but an unbelievable manager.

In training it was frustrating at times because some of the boys were diving and it did my head in, but you get used to it. It can be frustrating but it is the way they have been brought up and the way they play.

Getting in each other's faces and sprinting to the referee. I am not that type of player to do it in games, but it is what it is.

'Simeone has had a massive impact on me'

Kieran Trippier: I admire him - it comes down to respect. Everyone respects him because he respects his players - he has so much trust in his players.

You build that relationship on the training field and he is unbelievable around the place. The most important thing is how he was with players who weren't playing. He was so intense with them the day after the games and he just gains so much respect. I learnt so much.

I made it clear when I went there I wanted to improve my defending, and he worked me so hard on the training field throughout the time I was there on my own after the training sessions.

I respect him for that. He worked with me for hours - everything has made me mature as a person. Now I am at Newcastle and hopefully I can help them.

Simeone has had a massive impact on me. Look at the players there: Koke, Stefan Savic, Jose Maria Jimenez, I have learnt so much from them - because at Atletico Madrid he has like five captains and you watch these players every day, how they prepare for games.

Atletico Madrid is like a family. The manager is emotional, and during Covid, when we had to train individually, it really frustrated him because he is one of those hands-on managers who are so emotional. His speeches are unbelievable.

You just know Simeone will be flying around the dressing room before the second leg - he will be so intense. He will be telling the players how much it means to the club and to the fans.