Gerrard and Mourinho have never worked together during their respective careers – despite the former saying he had the chance to on four separate occasions.
Liverpool legend Gerrard even described Mourinho as his “dream” manager in 2015, and remains a fan of the Portuguese.
Mourinho has come under intense scrutiny during his Manchester United reign, with the club eighth in the Premier League table after 12 games.
But Gerrard believes “it would be foolish to write him off”.
When asked how he would describe Mourinho, Gerrard told The Guardian: “I think of one word: winner.
“He’s a winner. When winners feel that stuff around them is affecting their chances of winning then maybe the behaviour changes.
“But he’s still a world-class manager and he’s already won things at United. It wouldn’t surprise me if he won more trophies at United.
“I think it’s him doing things on purpose, to galvanise and get that siege mentality. It would be foolish to write him off.”