Since taking over at the Etihad in 2016, Guardiola has failed to guide City past the quarter-finals of the Champions League, which followed three seasons of failing to lead Bayern Munich past the semi-finals.
It is a disappointing return for the Spaniard after he won two Champions League titles in four years in charge of Barcelona from 2008-12 and Matthaus feels the he knows what the problem is.
The man who won 150 caps for Germany thinks Guardiola tries to be too clever in the big games, trying different systems, which is ultimately to his team’s detriment.
City were beaten by Lyon in the Champions League quarter-finals last month as Guardiola attempted an unusual 3-4-3 formation, which Matthaus believes was another example of his ego running wild.
‘He always wanted to show that he could do even better. I would like to tell him: Pep, you are a giant trainer – but please keep your system!
‘I would describe it as egocentric. Yes, that’s a harsh word, but it is due to what he did. At Bayern, Robert Lewandowski even had to play left wing once. That did not work out at all.’
Bayern picked up the Champions League trophy in August for the first time since 2013, the season before Guardiola arrived in Bavaria.