The cup competition represents the 'Red Devils' only realistic opportunity of silverware this season after elimination in the Champions League and their unlikely chances of catching Manchester City in the Premier League.
United saw off Brighton & Hove Albion at the quarter-final stage and will now face Tottenham for a place in the final on May 19.
However, their midfielder Matic does not believe that winning the FA Cup will be enough to save their season, arguing: "I think no. If we win the FA Cup it is good, but not perfect.
"You have four competitions in the season - if you win one for me it is not enough, but you always have to do your best.
"In the Premier League, when you are in the first four this is not perfect but is good to play for the Champions League next season. If you win the FA Cup I cannot say it is a successful season, but it's a good season."