Once he arrived in Rotterdam Collen started on the bench. Due to good play in training, he forced himself into the squad and played many good matches in the Dutch top flight as well as in the UEFA Champions League. However, a string of injuries and a long period of rehabilitation caused him to be sidelined until the end of the 2002 season. He was part of the Feyenoord squad that won the 2001–02 UEFA Cup, as an unused substitute in the final. When he was declared suitable to play again he was loaned out to NAC Breda but suffered another a season-long injury and returned to Feyenoord.