Manchester United v Manchester City
Marouane Fellaini scored goals against Tottenham and Manchester City Getty Images

Manchester United legend Gary Neville believes the trio formed by Daley Blind, Ashley Young and Marouane Fellaini on the left flank of manager Louis van Gaal's side will be the key to beating Chelsea when they face each other on 18 April.

After a difficult start to life under Van Gaal, United have rediscovered their best form to consolidate their spot in the top four of the Premier League, with a run of six consecutive victories against the likes of Tottenham Hotspur, Liverpool and Manchester City.

And even though summer 2014 signings Angel Di Maria, Radamel Falcao and Luke Shaw were deemed likely to play defining roles for United, it has actually been other players who have stepped up to the plate.

Neville believes Blind and Young have played a crucial part by replacing Shaw and Di Maria, while Fellaini, who had a poor debut season at Old Trafford, has used his aerial power to devastating effect.

"I think Blind and Young are both intelligent players. They understand their positions and they are picking up what Louis van Gaal wants. You have to put Fellaini into the mix as well, given where he's playing in that left channel and that's been a feature of Manchester United's play in these last few weeks," Neville said to Sky Sports.

"Against Tottenham it was the most outstanding element in United's game and I think it won them the game. It posed problems for Liverpool as well and it certainly posed problems for Manchester City on Sunday.

"Chelsea now have to prove that they can handle it on Saturday. The other three teams that they've played against haven't been able to handle it."

Fellaini scored goals against both Tottenham and Manchester City, and he received a standing ovation from the Old Trafford crowd in the latter match following an excellent performance.

"Fellaini is someone who needs special attention, there's no doubt about that," Neville added. "He needed special attention at Everton and it's the same at Manchester United."

The Sky Sports pundit believes United are arriving to the game in better form than the Blues but warns Van Gaal's side about the danger of Eden Hazard and Chelsea's set-pieces.

Neville said: "[Chelsea boss Jose Mourinho will] play the long game because his side aren't playing very well. United are playing better than them at the moment, but he'll want to stop that pattern on the left side. More often than not, when he pays attention to things, he does.

"That will give him Cahill, Terry, Matic, Zouma, Drogba potentially, and he'll think that he can win the game either by a bit of magic from Eden Hazard or a set-piece."