Two Real Madrid players must be careful in Estadio San Mames, Dani Carvajal and Casemiro are both just one booking away from suspension, with four yellow cards apiece currently.
The situation is a concern because, with both players key to Zinedine Zidane's plans, December poses some seriously challenging fixtures for Real Madrid.
Beginning with the trip to the Basque Country, Real Madrid face only two more La Liga games in 2017 but neither is easy.
Next Saturday, the always threatening Sevilla will visit the Bernabeu. Next up, on December 23 and after the club's participation in the Club World Cup, there is a Clasico against Barcelona which will be crucial if Zidane's men are to have any hope of defending their league title.
Casemiro and Carvajal both know that they have to be careful against Athletic on Saturday, in a game which is always played at high speed with tension.