Radamel Falcao
Radamel Falcao has scored just four goals for Manchester United this seasonGetty

Manchester United star Radamel Falcao has increased speculation over his uncertain future at Old Trafford with a mysterious message on his Instagram account where he said "there are times when you have to" make changes in life.

The Colombia international moved to the Premier League giants on transfer deadline day in the summer of 2014 after United agreed a loan deal with Monaco, with the option of making the move permanent at the end of the season.

But having since scored just four goals in 29 appearances for the club, it is unclear whether manager Louis van Gaal will decide to secure his services on a permanent basis ahead of next season.

The 29-year-old appeared to say goodbye to the Old Trafford supporters during the club's last home game of the campaign, in the 1-1 draw against Arsenal on 17 May, while he later tweeted: "Thank you so much for the incredible support of the Manchester United fans all season. Unforgettable."

And after club legend Paul Scholes predicted his departure from Old Trafford at the end of the season, Falcao has added his own input on the situation.

"To make changes and decisions in life is not easy! But there are times when you have to do it! Just risk it!" he wrote.

Reports in Spain have linked the striker with a return to Atletico Madrid, with some suggesting Monaco will offer Diego Simeone's side a swap deal that will see Falcao move back to the Vicente Calderon and Mario Mandzukic make the opposite trip to the Ligue 1 side.

Simeone coached Falcao during his time at River Plate and when asked about the possibility of reuniting with him at Atletico Madrid, he said: "I am grateful to all the guys who have been here.

"Falcao has been a reference for Atletico Madrid. Anyone who has gone through the club and has left a mark in the club like these two guys always will be seen in a special way. But this doesn't mean he will return. It is not easy.

"Falcao had an unlucky injury in a difficult moment because it was before the World Cup. But he is a strong guy. He is going to fight, he will probably leave his club [United] to compete again in another place where he can feel alive. Because Falcao needs to feel alive and competitive. As soon as he felt that he will respond again because he is still young."