United dominated much of the first half but couldn't make a breakthrough much to the frustration of the home fans.
The second half though was a much different story as Juan Mata scored the opening goal of the game 11 minutes into the second half.
Just as the game looked like it was going to finish 1-0, Marouane Fellaini scored a header to give United a crucial two goal cushion going into the game at the KC Stadium in two weeks.
United made a strong start but missed crucial chances
Jose Mourinho made seven changes to his team for the game with the likes of Paul Pogba and Henrikh Mkhitaryan returning to the starting lineup as Mourinho showed his intent to try and win the game.
It looked like it aswell on the pitch as United almost went in front within three minutes of the game starting when Mata forced Eldin Jakupović into making a fantastic save.
Not long after that, a lovely flowing move from the hosts ended with the ball falling to Mkhitaryan in the box unmarked but he put his right footed shot wide of the goal when he should have done so much better.
The frustration of them early chances began to show though as the hosts had all of the possession but struggled to break through a very defensive Hull team.
Hull almost scored against the run of play
The visitors only created one chance of note during the half but it was the closest anyone came to scoring a goal when a Robert Snodgrass free kick was headed< onto the post by Adama Diomandé, who was so unlucky to see his effort not go into the back of the net.
Therefore at half-time, Marco Silva will have been very happy with his Hull side for the application they showed in defence as they showed fight in order to not concede any early goals to a rampant United team, who came into the game on a brilliant run.
It didn't last the whole game though unfortunately for the visitors as the second half started the same way as the first as United came close to scoring once again when a lovely through ball from Pogba found Rooney in the box but the striker put his shot just wide of the goal.
Mata gave United the crucial breakthrough
The hosts though did finally make the breakthrough when an Antonio Valencia cross found Mkhitaryan in the box, who in turn headed the ball across to Mata, who put the ball into an empty net to get the crucial breakthrough.
After the goal, United were in complete control of the game without creating a number of big chances with Hull penned back in their own box for the whole of the second half.
Pogba was very unlucky to not double United's lead when he curled a free kick from the edge of the box towards goal but the ball came back of the post with the goalkeeper beaten.
Fellaini added a second before the end much to the delight of Mourinho
Just as the game looked like it was going to finish 1-0, Fellaini on as a second half substitute, headed the ball into the back of the net after a great cross from Matteo Darmian to give United a comfortable cushion going into the second leg at the KC Stadium.
Anthony Martial came close to adding a third goal in injury time but saw his goalbound shot well saved Jakupović to keep the score at 2-0 at the end of the game.