Although Renault have taken much of the stick for Red Bull's troubles, Daniel Ricciardo concedes their problems go beyond the engine.
Ricciardo and new team-mate Daniil Kvyat have struggled to match the front runners this season, falling well off the pace of both Mercedes and Ferrari.
The team's best results have been the Aussie's two P6s while last time out in Spain they were once again lapped by the race winning Mercedes.
Renault have received a great deal of the criticism for Red Bull's faltering form, however, Ricciardo says the RB11 is as much to blame.
"I don't want to sound too critical but I don't think there's one outstanding excuse," he explained.
"For whatever reason, the puzzle hasn't quite come together yet and therefore the car's not working as well as it should be.
"I think we knew even before Spain but that highlighted it's not only engine – we're aware of that, putting our hands up and saying it's not where we should be.
"The last four or five years with Red Bull the stand out was downforce – even last year we were pretty good at high speed, it was our strength.
"“This year we're not better than anyone at high speed, if anything I think we're slower than the top guys.
"For whatever reason we've not taken that step forwards and other guys have. Everyone in the team knows and we need to figure out why and fix it, it's not just Renault.
"The car they've built is not working as expected but the ins and outs, I'm not sure."