Manchester United youngster, Marcus Rashford scored twice against Liverpool on Saturday in the Premier League, to give the Old Trafford side a 2-1 victory over their arc-rivals.
The win meant United have opened a five-point gap on Liverpool, who were just two points behind on the standings.
Rashford was handed a rare start by Mourinho. He had not start a game for the since boxing day.
First, Lukaku's header from David de Gea's clearance found Rashford charging into the Liverpool's box. He cuts inside Trent Alexander-Arnold and fired into the bottom corner for his first goal.
The Belgian striker was again instrumental for United's second goal. He held up the ball from another goal-kick before feeding Juan Mata. Though the Spaniard and, could not get to shot the ball, it graciously fell to Rashford to score via a slight deflection from Alexander-Arnold.
Liverpool could have fallen further behind when Mata volleyed acrobatically wide from an Alexis Sanchez's cross.
Jurgen Klopp's side improved dramatically at the beginning of the second half. Manchester United Defended in numbers, which made it difficult for the visitors to open up their hosts.
It took an own goal for the Reds to reduce the deficit, when Eric Bailly turned in a Sadio Mane's cross past De Gea while attempting to clear at the near post.
The goal gave Liverpool hope, but the team failed to find the equalizer, despite six minutes of added time.
Manchester United next face Sevilla on Tuesday in the second leg of the Champions League round of 16.
However, Liverpool are through to the next phase of the competition after eliminating Portuguese Champions, FC Porto.