Red Bull were left baffled by their lack of pace at the European Grand Prix on Sunday, especially considering their decent showing in qualifying.
Daniel Ricciardo started from the front row on the grid for the race in Baku, but the Australian could only manage a seventh-place finish after struggling with grip around the street circuit.
His Red Bull appeared to show good early pace but it dropped off immediately after several laps, with hopes of a podium evaporating with it.
Team-mate Max Verstappen finished one place behind in eighth in a difficult day out for the Red Bull pair.
"We went back quite quickly. We just had rear tyre issues, couldn't keep the grip in them, couldn't keep the temperature out of them," Ricciardo said.
"It felt like they were getting really hot, wheel-spinning in fourth gear.
"It's a bit unexpected, we race at some hot circuits across the calendar. Singapore, for example, is always one of our stronger ones. So we didn't expect to suffer with that today, but that was our biggest limitation.
"We need to understand why. I think then, the two-stop wasn't the plan but we were forced to do it. There was nothing in strategy, we couldn't have done anything better with what we had. That was just the pace today."
Red Bull boss Christian Horner conceded the team must do some homework to find out just why the tyres struggled so heavily in Azerbaijan.
"It's a difficult one to understand. On the supersoft and the soft we had very high degradation. We just couldn't do the lap times," he said.
"So then we went on to the hardest compound, and the car came alive on that compound. Max has set the third fastest time of the race, so a little bit of homework to do to understand what's happened there.
"Last week it was too cold, this week too hot. There's something that we've missed in the last two grand prix that we've got to get on top of.
"We've qualified well here, and the first two laps Daniel had no problem going with Nico [Rosberg] and then suddenly, bang, the tyres have started going off. It looks more accentuated on our car than any other."