Daniel Ricciardo admitted he was mystified by his lack of pace as he slumped to his worst race finish since he joined Red Bull at the start of 2014.
Ricciardo started from ninth place but slipped back and crossed the line a lowly 13th, 12 months on from his maiden victory at the Canadian Grand Prix.
"It’s been a strange weekend for me and I am a little confused about today’s race," he said.
"I was lacking pace and we are not sure why. There was nothing that felt especially wrong but we just couldn’t get any pace out of the car.
"I had a few set-up changes compared to Daniil [Kvyat] but that doesn’t explain the difference in pace. It is something we will look at to understand what the cause was."
Kvyat collected ninth position and conceded that it was the best result possible.
"It was a tough race because the Mercedes powered cars had a clear advantage over us, but we managed to keep two of them behind us today which is the maximum we could have done," he said.
"Two championship points is the best we could have achieved."