Memphis Depay has said he was upset with his substitute role under Louis van Gaal but has vowed to regain his form with Manchester United next season.

Depay, 22, was one of Van Gaal's star signings last summer, joining the Red Devils for a reported £25 million fee, after a successful time at PSV Eindhoven where he scored 50 goals in 124 appearances for the Eredivisie giants.

With 16 starts and 13 substitute appearances, Depay's season ended with Van Gaal dropping him entirely for their FA Cup final triumph over Crystal Palace last weekend.

The Dutchman refuses to look back as he starts preparing for life under Jose Mourinho, who was appointed on Friday as the new manager to replace Van Gaal.

"It's not been a bad year, but it's not been a good year," Depay told Unscriptd. "It's been right there in the middle.

"I have more expectations from myself and the fans as well, that's normal.

"It's been new for me, this season, to play in the Premier League. The experience that I get this season is important, also the things I have to deal with.

Memphis Depay managed 16 starts and 13 substitute appearances in his first season with Manchester United. John Peters/Man Utd via Getty Images

"Sometimes I've made a mistake or I haven't played good for a game and you get put on the bench. It's new for me as well.

"Last season I was playing and I was scoring every game and this season it's 50-50.

"I have some games on the bench for 90 minutes. That's new and it's hard. Of course it pissed you off, to be honest, sometimes.

"But you need to keep going and keep believing in yourself because you are the first person who must believe in yourself.

"No matter what, you have to always keep your chest out. Sometimes it's hard, it's really hard.

"But I'm still young, 22. If you believe in something that you can achieve, I think you will make it if you put everything into it.

"That's my motto: dream, believe, achieve. I don't want to give up on anything."