Man Utd star all smiles with Ander Herrera, Juan Mata at trainingMan Utd star all smiles with Ander Herrera, Juan Mata at training

Antonio Valencia was certainly pleased to be back at Carrington training ground as the Manchester United midfielder posed for a selfie with Ander Herrera and Juan Mata on Monday.

The Ecuador international has plenty to prove to new manager Jose Mourinho after an injury-hit campaign under Louis van Gaal in the 2015/16 Premier League season.

According to Sky Sports journalist Guillem Balague, the 29-year-old versatile wing-back is a target for newly-promoted Middlesbrough in the summer transfer window.

However, Valencia, who moved to United from Wigan Athletic in a £15m deal in 2009, was in high spirits with his team-mates Herrera and Mata outside the club’s training ground on Monday.

Valencia posted the above photo on his Instagram page and wrote the following caption:

"I feel very happy in my first day of training. @anderherrera @juanmatagarcia @manchesterunited"

Mata is another United player who could be facing an uncertain future under Mourinho after the 53-year-old sold the Spain international to the Red Devils from Chelsea in 2013.

According to The Daily Express, the World Cup winner is up for sale and is a target for Premier League rivals Everton in recent weeks.