German international Koch missed the weekend win at Burnley as a precautionary measure due to a niggle in his hip and he will not play again in the league this term.
Meanwhile, Poland midfielder Klich, impressive in the fine recent victories over the Clarets and Spurs, will also not be involved in the matches against Southampton and West Brom as he recharges his batteries ahead of tournament involvement next month.
Pablo Hernandez will be assessed in training ahead of a decision being made as to whether he will be involved in Tuesday night’s game at Southampton.
Bielsa, speaking ahead of the long trip to the south coast, said: “Koch has been given early leave with the potential for him to be called up or not called up for the German national team. The injury he has is not important. And we did not want to take the risk of him playing and making it worse.
"I don’t know whether he is going to be called up into German national team or not. What I did want to say is that we anticipated one week of his holidays not linked to whether he is going to be called up or not. He has a small niggle. We did not want to run the risk of a small niggle being aggravated into something bigger.
“We anticipate his holidays in the same way as we did for Klich. In this case, he was not injured, but we could anticipate his holidays for one week and that’s why we took that decision. With relation to Pablo, we are going to see how he is in training."
On the situation with Klich, Bielsa added: “No, he is not injured. The evaluation that I make over the campaign are for the needs of each player. In the case of Klich, the decision I made is the most favourable for him."