Erik ten Hag played Jadon Sancho in the No.10 role as he felt there was space in Leicester's midfield for Manchester United to exploit.
Sancho replaced Alejandro Garnacho at half-time with United fortuitously ahead by one goal after 45 minutes that Ten Hag branded "rubbish".
Marcus Rashford gave United a two-goal cushion in the 54th minute and Sancho made it 3-0 in the 61st to effectively kill a contest Leicester had dominated in the first half.