At Old Trafford today the game was effectively over before the break, with United scoring four first half goals.
Defender Chris Smalling grabbed the first with a towering header from a corner, with Mata adding a second with a slick finish.
The Reds compounded the Foxes’ misery when Rashford bundled in a point-blank shot and record-signing Paul Pogba thumped in United’s second header of the game.
While Leicester grabbed a 59th-minute consolation via a wonder-strike from Demarai Gray, it was too little too late from Claudio Ranieri’s men.
Rooney did appear for his side in the 83rd minute, but failed to make an impact and the match finished 4-1.