He went on to spend five seasons in La Liga with the former club, making his debut on 2 September 1973 in a 2–1 away loss against RC Celta de Vigo.
[1] He added 11 appearances in the runner-up run in the 1976–77 edition of the UEFA Cup, featuring in the 2–1 home win over Juventus FC in the second leg of the final.
He scored a career-best (at the professional level) ten goals in his first year, but his team could only finish in 14th position; until his retirement in 1983, aged only 30, he competed solely in that tier.
After leaving Athletic, Amorrortu became manager of SD Eibar also from the Basque Country (second tier), signing a two-year contract with Real Sociedad on 3 June 2004[5] and being fired in late January 2006.
[6] From 2006 until 2011 he acted as director of Atlético Madrid's academy[7] before returning to the same role at Athletic Bilbao,[8] departing at the end of 2018 when Aitor Elizegi was elected president and implemented personnel changes.