The former Barcelona stalwart has hit out at his young striker, complaining about his selfishness on the pitch and telling the Swede he needs to work harder.Feyenoord coach Ronald Koeman has spoken out against John Guidetti\'s lack of work ethic after his side\'s 3-1 win over NAC Breda on Saturday.The exciting forward, who is currently on loan from Manchester City, has been a constant concern for his boss this term, and the one time Valencia man has finally spoken out about the attitude displayed by his young starlet.“John [Guidetti] will be best served if he starts to work harder on the field,” the 49-year-old former Dutch international told De Telegraaf.“He needs to stop being so concerned with his own game, and more with those of his team mates.”The 19-year-old Sweden international has been on sparkling form this season with 19 goals in 21 games, and has attracted the attention of Bayern Munich.