Louis van Gaal insists Radamel Falcao is not fit enough to start for Manchester United and is “not interested” in whether he is unhappy at being benched.

Falcao, currently on a season-long loan from Monaco, has made just three starts and four sub appearances in the Premier League.

The 28-year-old Colombia international is expected to be a substitute for the trip to Southampton, after the United manager confirmed Wayne Rooney is fit and “will play.”

Van Gaal said: “Falcao needs match fitness. He can only play for 20 minutes.

“I have selected him despite that but the rhythm of the game in the Premier League is the highest.

“It would be a better contribution if he played with the second team but I cannot do that because on Tuesday Rooney was injured for the match against Stoke.

“I had to adapt to the needs of selection. I am not interested whether he is unhappy being on the bench. He has to follow my philosophy. I am here because of that.”