The retired footballer - who won six Premier League titles with the Red Devils, as well as a Champion League trophy and two League Cups - insisted the lineup for the next campaign is "mouthwatering".
He told FIVE's YouTube channel: "If I was looking at the team now and you have McTominay with Bruno [Fernandes] on one side of the three and Pogba on the other...
"Rashford up front, Martial on the left, James or Sancho if they buy him on the right.
"You can't tell me other midfielders aren't going to be thinking, 'If these lot are on fire today we're going to have to be on a game, it's going to be a hard day work for us'.
"There's ability there, it's ridiculous. If they can find that cohesion, the team set-up for them to flourish, it's mouthwatering what could happen."
However, the former England international acknowledges it's not that simple for United, particularly with Pogba's future uncertain.
Rio added: "It's if, buts and maybes. We need Paul Pogba fit, we need him in that team and to see what he's like to see if the relationship can be built with the players and the players Ole is acquiring now.
"It's up to Paul Pogba, Ole Gunnar Solskjaer and the powers that be at the club whether Paul Pogba stays at the football club, then we see.
"Look, I want him to stay, I'm a Manchester United fan. I want to see him wearing the red shirt so we can compete for the league and other things."