Well I missed it but luckily there is iMiasanmia:

Tuchel explains his decision to start Choupo-Moting ahead of Müller: “Köln are very strong in set pieces - and Choupo is very good at defending set pieces. Offensively, he’s really good in the air. We expect a very high pressing from Köln and that’s why we can also use Choupo for long balls because he can hold the ball well. We simply see other reasons in training. Choupo was in training all week. It’s also important to find a mix between those who are in the rhythm of the national team, but also those who, like Choupo, have trained well all week”