Red Bull cannot expect a boost from the Monaco Grand Prix's lower power demands and must 'get its act together' before Formula 1 reaches Singapore in September, says Adrian Newey.
Last year Red Bull took Monaco pole with Daniel Ricciardo and was set for victory before a pitstop error, in one of the team's most competitive performances of the 2016 season.
Newey said that was down to a chassis advantage that offset Renault's engine performance deficit to Mercedes, and Red Bull is no longer in that position.
He fears missing the opportunity to shine in Monaco means Red Bull will be on the back foot until F1's next low-speed street track in Singapore.
"Last year we had a good chassis," Newey told Autosport.
"So at Monaco, which is less engine dependent, we were able to shine.
"This year we haven't got the best chassis.
"So it won't be the opportunity it was last year.
"I guess we've got to get our act together between now and Singapore and use that as the next chance."
Red Bull introduced its first major update package of the year for the Spanish GP a fortnight ago, but still finished over a minute behind Mercedes and Ferrari in the race.
"I think the package was a small step forward, which is what we expected," said Newey.
"It got vastly overhyped by the press.
"We know we've got some work to do, we know what we need to do, so we've just got to get on with it.
"It was never going to be the magic bullet, and there is no magic bullet.
"It's the usual thing, just chipping away at it."
Team principal Christian Horner emphasised that both Renault and Red Bull had plenty to do.
"Everyone is just focused on getting ourselves into a competitive position," he said.
"Of course the engine arguably is even more of a factor nowadays, because you're running even longer at full throttle.
"Renault are making strides with that. They've obviously got their own limitations.
"As far as the chassis is concerned, the bit we can control, I don't sense any frustration, I just sense a determination to get performance onto the car quickly."