I would like to reply to his post with a strict definition just to make my post a bit more interesting. I define players who made the wrong move as those who went to another club but his career went downwards so much that he became far below his previous level. So I am excluding guys like Torres (doing decent for Atletico by turning from Complete Forward to Target Man reached double figures in goals for Atletico for the first time in 5 years), Balotelli (rediscovering his touch even though you can say that Ligue 1 is rubbish), and Zlatan (rediscovered his form after leaving Barcelona). I am also excluding overweight, greedy and unmotivated players who are using their past reputation to con Asian clubs to pay for their services and later blame the club and the league for his lack of success (JERMAINE PENNANT, yes, I am looking at you).
Aleksander Hleb: Arsenal to Barcelona
One of the most feared inside forwards, he was one of the best players at Arsenal and in the world. He went to Barcelona and sat on the bench for a season, and seemed to have lost his mojo. He never reached the same level when he went on loan and was moving clubs yearly for a few years until he suffered an injury. He is now moving across clubs regularly as well.
Park Chu Young: Monaco to Arsenal
Wasn't he a first team player at Monaco? A last minute panic buy, he never really started for Arsenal. He was not even on the bench. He got loaned to several clubs and never made the grade too. He became deemed to be not suitable for European level after this and he has moved back to the Korean league.
Julio Baptista: Sevilla to Real Madrid
My friends called him 'the Animal'. They talked about how strong and powerful he was and how he ripped center backs apart. Lost his magic after Sevilla and he was being moved around from club to club. I saw him and Richard Dunne going for the same ball, and he was completely destroyed by Richard Dunne. Maybe the La Liga defenders he faced were weaker.
Francis Jeffers: Everton to Arsenal
Poor guy. Got injured so often at Arsenal that he hardly even played. Was labeled one of England's best prospects but went to zero in a span of a few years. He then went to play for clubs in Australia.