The German went off at the second Degner corner before recovering to finish third in both sessions.
"I think it was not really a big mistake. It was maybe at that moment I was not 100% awake, and mistakes around here can be quite costly.
"I went off and tried to come back, tried to slow the car down as much as possible but didn't make it and hit the wall slightly.
"It was not a big impact but it did some damage the car. It's not perfect and it did affect our run plan a little bit, but I think we had a solid afternoon."
The 24-year-old needs only one more world championship point to secure back-to-back world titles.