The former Liverpool man does not think the right-back will end up at Old Trafford because of the options Jose Mourinho already has available to him.
Antonio Valencia and Matteo Darmian are at Old Trafford already and Nicol doesn’t think Roberto is any better.
“For him it would be a hit but it’s not going to happen,” he told ESPN FC.
“I don’t see Roberto as any better than Valencia and certainly you’ve got Darmian who can play there.
“The jury’s out whether he’s a right back or a right midfielder. I just don’t see how this happens.
“He’s definitely going to leave but I don’t think it’s to Man Utd.”
United started their Premier League campaign by thrashing West Ham 4-0 at Old Trafford last weekend.
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Romelu Lukaku netted twice, while Anthony Martial and Paul Pogba were also on target.
United return to action on Saturday when they travel to Swansea in the top flight.
Roberto has failed to score in his 95 La Liga appearances for Barcelona.
