Jamie Redknapp says Jose Mourinho will not start Marcus Rashford for Manchester United's clash against Manchester City at Old Trafford on 10 September. The former Liverpool midfielder has backed the Portuguese tactician to use the teenager as an "impact substitute" at Old Trafford on Saturday.

The 18-year-old was not included in the England senior squad by their new manager Sam Allardyce, which saw him being demoted to the Gareth Southgate's Under-21s. He was the star player in his side, scoring a hat-trick in Young Lions' 6-1 victory over Norway.

Mourinho has already confirmed he has a fit squad to face Pep Guardiola's side, meaning there would be heavy competition for a place in the starting lineup. Zlatan Ibrahimovic and Wayne Rooney are assured to start against City.

Rashford scored the winner after coming off the bench against Hull City before the international break. Redknapp claims it will be easier for Mourinho to drop Rashford instead of the two experienced attackers and believes the forward to be an impactful player while making a substitute appearance.

"It was an important moment for the kid and will make him feel a little bit taller. He'll believe in himself more than ever and will go back to Manchester United feeling like a million dollars," Redknapp told Sky Sports.

"There will be confidence flowing through his veins. He'll feel closer than ever to be able to go to his manager and say 'I'm ready now'. But I don't think he will start in the Manchester derby.

"I see him being used as an impact substitute - as he was when he scored the winner against Hull a fortnight ago — and I don't think it's a difficult decision for Jose Mourinho.

"That's because things have gone well for Manchester United so far this season. Zlatan Ibrahimovic is a big-game player and you wouldn't dream of leaving Wayne Rooney out at the moment. There's enough evidence to justify keeping Rashford on the bench for now.

"It's easier to keep a 18-year-old happy when he's not playing than it would be to keep Rooney or Ibrahimovic happy. If he left one of those two out of this game he might lose them for the rest of the season.

"I don't think that's Mourinho's game. He's too clever and astute for that. He will tell Rashford 'well done, you're amazing and I need you to be ready to come on for me on Saturday.' He'll tell him he can be the matchwinner in the derby."