The Finn got off to a good start, but finished nearly a minute behind race winner Max Verstappen and was overtaken by Sebastian Vettel who start from the back of the grid.
Bottas was surprised to see Mercedes struggle with pace at a track expected to suit them, but has admitted himself that he is not driving at his best.
“It was definitely not the race weekend we were expecting coming here,” Bottas said. “Because we really could have been strong here but since Friday we have been struggling. Today was the same, just lacking pace.
“I think as a team we have been struggling to get the car good enough for these conditions and then I think it’s a different story on my side for why I’ve been lacking pace.
“I think there’s various reasons which we need to find out. I’m definitely not at the best at the moment, or at my most confident state.”