Mayweather tried more mind games on Wednesday when he claimed the Irishman has the advantage, but Berto admits the UFC star has a chance.
McGregor will box for the first time as a professional and he will be hoping to make history at the T-Mobile Arena.
Mayweather is widely expected to win every round at the age of 40 but Berto insists that it will not be plain sailing for his former rival.
Berto told MMA Hour: "I see Conor coming in there really showing that bravado, showing that cockiness and showing that he's really there to fight.
"And somewhat trying to steal the stage from Floyd just with his antics and get Floyd into a mind-game situation, have him pulling some type of mistakes and then catch [Mayweather] with a big shot.
"And [McGregor] could stop him."