Taibi feels Onana is letting himself down at United and may not suit Premier League football.
He told The Sun: “I’d be straight to the point and tell him, ‘Andre, you are one of the best keepers in Europe but in the Premier League, you are under- performing.
"Block out criticism, do some soul-searching, press the reset and go again. And if things don’t change by June, move on’.
“I think subconsciously the United environment isn’t ideal for him and when a marriage is showing cracks, it’s pointless to continue.
“Sometimes things don’t work out at a team and it’s best to go separate ways, which would not be a failure.
"For me he’s a strong goalkeeper who finds himself in a situation where he can’t show his skills because he is not cut out for the English game.
“He’s only suited to the Prem when it comes to his ball-playing ability and structure.”
Taibi added: “Andre’s a better fit for an Italian or French team.
For English football you need a goalkeeper who is more imposing, regularly comes off his line using his fists and with a different saving technique.
“In his place I’d not have left Inter, where he was a big-shot. He made a calculated risk thinking he would slot in seamlessly at Manchester United but it backfired.
“But even though he hasn’t lived up to expectations he remains a top keeper, one of the best in Europe.”