Bastian Schweinsteiger has revealed David de Gea was furious at him for comparing the Manchester United stopper with Manuel Neuer.
The retired Germany international won the World Cup with Neuer in 2014 and spent nearly two seasons playing alongside De Gea at Old Trafford.
Speaking to BBC Radio 5 Live, Schweinsteiger remembered: "When I first came to Manchester United De Gea said, 'Tell me, am I better than Neuer?'
"I was like 'No, you're not. It is a different level.' He was angry, but I explained why. Whenever he had a great game he would ask me again, I would still say he wasn't on that level."
Schweinsteiger joined United in the summer of 2015 after making 500 appearances for Bayern Munich, many of which were alongside Neuer.
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The German stopper, 35, has enjoyed a tremendous career, winning nine Bundesliga titles, five German Cups, the Champions League twice and many more honours.
De Gea, meanwhile, hasn't lifted silverware since United won the Europa League in 2017 and lost his starting spot for Spain to Unai Simon at Euro 2020.
The Spaniard's form has improved significantly since the summer, although United are currently struggling under current boss Ole Gunnar Solskjaer.
The Red Devils have picked up just one point from their last three Premier League games ahead of a huge clash with Liverpool at Old Trafford on Sunday.
And Schweinsteiger has questioned whether the former Molde and Cardiff manager can end the club's five-year trophy drought this season.
The German added: "Manchester United are still in progress. Ole Gunnar Solskjaer keeps mentioning that. It takes too long though for me in my eyes.
"If you look at Manchester City or Chelsea and the impact that Thomas Tuchel had on them - it was unbelievable.
"He knew exactly what the players needed to perform and they have a strategy and a DNA. They have more in their game.
"The experience of Cristiano Ronaldo and Raphael Varane will definitely help the team, but the question is how much are they involved in the tactics of the team.
"It is still not 100 per cent clear to me if Manchester United are going to be successful or not.
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"They have great names like Paul Pogba and Cristiano Ronaldo, and I think that Marcus Rashford will help them a lot in the future because he has been injured. It has not been easy for them.
"But if you compare their football to other teams like Chelsea, Manchester City, Liverpool or even like Bayern Munich it is not on the same level at the moment.
"United can always hurt you in one game, that is clear to me, especially at Old Trafford."
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