Jose Mourinho's men took a 2-0 lead in the game thanks to goals from Zlatan Ibrahimovic and Jesse Lingard but they were pegged back to 2-2 just after half-time.
Manolo Gabbiadini scored a goal either side of half-time to get his side back in the game which they full deserved to be in and just as it looked like the game was going to extra time, United won it with three minutes remaining.
Once again it was Ibrahimovic who came up with the big moment for United as he headed home in the 87th-minute of the game to hand United the win.
Despite the win though, their is still a few things that stood out during the game that could be worked on in the coming weeks.
Heavy reliance on Ibrahimovic
Ibrahimovic once again was the match winner for United at Wembley but it is now becoming a problem for the team as it seems he is the only one who gets the goals. The striker notched up his 25th and 26th goals of the season which is amazing for him but he is still the only player in the team to get to double figures this season. The good thing though with Ibrahimovic is that he seems to enjoy the pressure of being the main man but if he was to go on dry spell from now to the end of the season it could turn out to be a real problem for United if others don't step up.
Mkhitaryan makes the team so much better
One thing that was very clear from the final was that United really missed Henrikh Mkhitaryan, who missed the game due to injury and could be out for a while longer yet. It's such a pity that the midfielder picked up the injury at such a crucial time as he was just starting to really show what he was all about at United. During the match against the Saints, United really missed his driving runs which really cause teams so much problems and allows United to dominate games much more.
Smalling makes the whole defence nervous
Chris Smalling may have led United out at Wembley as captian but his presence in the back four caused a whole lot of nervousness. Smalling has really struggled this season to repeat what he done under Louis van Gaal last season and whenever he is in the team, the whole United defence looks so much weaker than it should be and they were lucky to not be punished more that they were during this game. Phil Jones needs to come back quick to the team if they want to achieve more success this season.
Pogba only flourishes in a three man midfield
Paul Pogba failed to make a real impact in yet another big game for United. It wasn't fully his own fault though as when he has been played in a two man midfield this season, he is restricted to what he does for the team. It changed a bit in the second half when Michael Carrick came on and the hope is that with that in mind, Mourinho will hopefully utilise Pogba right to get the best out of him as he makes the team tick if he can keep going forward and do what he does best.
Rooney looks like the forgotten man at United
Wayne Rooney was back in the United squad for this game but he didn't play any part in the game. It shows just how far he is now down the pecking order at United that when they went in search of a winning goal he still sat on the bench. It is a pity that someone who is such a legend at the club is now not the same as he was and it very much looks like he will leave the club in the summer which he will do on good terms giving all he done for the club.