In the 1980–81 edition of the European Cup, Díaz scored both goals in a 2–0 home win against FC Spartak Moscow in the quarter-finals, after coming on as a substitute in the second half of the second leg, sealing the "Merengues"' qualification 2–0 on aggregate. After the 1984–85 campaign, aged 31 and having just won the UEFA Cup – he did not appear in any of the final games against Videoton FC, however – he signed with fellow top-flight side Racing de Santander, netting a career-best ten times in his first year but suffering relegation in the following.