Daniel Ricciardo says excessive tyre degradation caused Red Bull to switch to a two-stop strategy during the European Grand Prix.
Ricciardo started from the front row of the grid and maintained his position across the opening couple of laps, before he was demoted by Ferrari's Sebastian Vettel.
Ricciardo switched from the Super Soft to the Soft tyres but continued to struggle and required a second stop, during which he took on a set of Mediums, recovering to seventh place.
"We were forced that way, the intention was to one stop but with the Super Softs, the first two laps were looking pretty good," he said.
"I stayed with Nico [Rosberg], Seb wasn’t able to attack but it turned very quickly, I had wheel spin a lot and there was no way out.
"The intention with the Soft tyre was to get to end but we had the same balance.
"With Mediums we picked up some pace but with two softer compounds we were nowhere, it’s a shame, I thought we put ourselves in a position to fight but pace wasn’t there."
Ricciardo said the problem with the tyres came as a surprise to Red Bull.
"At the moment it’s an unknown [issue], for me it felt they were getting too hot and couldn’t generate grip, we didn’t expect it," he explained.
"[We're] usually good on tyre wear, when it's hot, Singapore is usually our strongest circuit, everyone's a bit surprised but we’ve got enough people in the team to understand, hopefully the next ones are more predictable."
Red Bull team-mate Max Verstappen encountered the same problem and mirrored the strategic approach to take eighth.