Sainz spent most of his career with Real Madrid, either as a player, or a head coach.

[1] As a player with Real Madrid, Sainz won 4 FIBA European Champions Cup (now called EuroLeague) titles (1964, 1965, 1967, 1968).

As a player, Sainz was a member of the senior Spain national basketball team.

As a head coach with Real Madrid, Sainz won 2 FIBA European Champions Cup (now called EuroLeague) titles (1978, 1980).

This biographical article relating to a Spanish basketball figure is a stub.