Athletic Bilbao coach Ernesto Valverde was left frustrated after their 3-1 defeat at Atletico Madrid.
The match was marred by alleged racist insults aimed at Athletic forward Nico Williams.
Valverde later said: "In our fields we have a big problem, which is education. This is already out of touch and is an issue that is out of the ordinary. It was a small incident and we hope it does not happen again.
"When you lose you don't have a good feeling. We dominated part of the game and I think that for a good part the draw was fair. In a steal of the ball in the second half they scored our second goal and in a rebound they scored the third .
"There is the League ahead and five more games. Nothing has been said, even though we are at a disadvantage that we would not like to carry at this point."