 Gurpegui was banned for two years on 3 November 2003, for testing positive for nandrolone in a 1 September 2002 game against Real Sociedad (2–4 away defeat, scoring both goals) the previous season.The ban was initially suspended after repeated appeals, with the player claiming that his body produced nandrolone naturally, but the appeals were in vain and he eventually was forced to serve his sentence, which ran until 23 April 2008; Athletic Bilbao, however, neither released the player nor took his number from the official squad, and he returned to action in a 0–3 away loss to Real Madrid, four days later.In the 2008–09 season, Gurpegui was used mostly as a backup due to the emergence of youngster Javi Martínez, but regained his starting position in the following years, precisely alongside Martínez.