 He started playing football for local Sociedad Deportiva, going on to appear in three Tercera División seasons with the team.In summer 1974, José Diego was signed by neighbouring Real Sociedad, making his La Liga debut on 7 September (two months before his 20th birthday) in a 3–2 home win against FC Barcelona and finishing his first year with eight games.From the following campaign onwards he became a very important unit for the "Txuriurdin", going on to contribute with 96 matches and seven goals in three seasons combined as they won the national championship in 1981 and 1982, adding the second position in 1980.