That's according to Bayern Munich legend Lothar Matthaus, who believes that the City manager has to "rightly listen to the harsh criticism from all sides."
Guardiola lifted the Champions League title twice during his remarkable managerial spell at Barcelona from 2008 to 2012.
But the 50-year-old Spaniard has faced scathing criticism for failing to lift Europe's top-tier club trophy during his subsequent spells at Bayern Munich and City.
Guardiola led City to their first Champions League final last weekend against Chelsea at the Estadio do Dragao in Portugal.
Ilkay Gundogan was deployed in a deep role as the former Barcelona boss surprisingly left Fernandinho and Rodri on the bench.
Guardiola's tactical decision to not use a defensive midfielder came back to haunt him as a Kai Havertz winner fired Chelsea to the Champions League trophy.
Matthaus pulled no punches towards the City head coach and slammed Guardiola's decision to not opt for a defensive midfielder.
The 60-year-old German told Sky Germany: "With his line-up, he stole the Champions League from the club and the fans and he has to rightly listen to the harsh criticism from all sides.
"I am sure that there will be internal discussions about whether to part with him. The players will doubt him since that final.
"He had to try something again, present an imaginary ingenuity at the worst possible moment and totally deserved to lose.
"How can you play without a defensive midfielder in the most important game in club history, who was on the pitch in almost every game of the season, who ensures the balance, who gives everyone involved the necessary security?
"Why did he leave Rodri and/or Fernandinho out, start six attacking players and also play without a centre-forward?"
Sergio Aguero's brother also hit out at Guardiola after the Champions League defeat, saying that he never wanted the Argentine club legend in his team.
Despite the Champions League loss, Guardiola did capture the League Cup and the Premier League title with City in the previous campaign.
And the City boss is reportedly preparing a squad overhaul in the summer as eight players at the club could be sold ahead of the new season.
Featured Image Credit: PA
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