Valtteri was the first to swap to the UltraSoft in the evening session and went second fastest behind Lewis, only to be shuffled down to P4 as the Red Bulls improved.
"This was a difficult day for us, I think we are missing some pace," said Valtteri. "We were making big setup changes between the first and the second session, but still didn't quite find the right setting.
"There is plenty of work to do from what we learned today. I was struggling with the overall grip and the balance of the car.
"The car felt quite nervous, so it's not so easy to trust the car when you push. That's the main thing we need to work on so that I can build up my level of confidence."