He said: "I've just not got the heart for it any more and I don't see the point in going through the motions.
"I've had a lot of knockbacks in my time but this has nothing to do with injury.
"I just don't enjoy it anymore."
Barcelona head coach Luis Enrique has made it clear he wants Manchester United target Pedro to stay at the Nou Camp this summer.
Much has been made of Manchester Uniteds chances of once again being in the running for the Premier League title by fans, players and pundits alike.
Manchester United are continuing to spend this summer and the arrival of player number six could be just hours away,
Augsburg defender Baba Rahmans move to Chelsea edges ever closer as the player is said to have agreed personal terms with the Blues.
Most neutral's will agree that Arsenal's pre-season has been an impressive one.
Liverpool are close to completing a deal for Barcelona starlet Adama Traore with the player due in Merseyside to complete