Nico Rosberg sounded distinctly rattled when talking about the pace of the rival Red Bull cars in Thursday's free practice sessions at Monaco, which saw Daniel Ricciardo some six tenths faster than the two Mercedes cars.
"It's very simple, today they were faster than us," said Rosberg, who currently leads the 2016 world championship points standings.
"It's a bit challenging out there in general, but that's fine. It's been a good day. Just Red Bull is quicker than us so need to see if we can find some more pace.
"Definitely surprising how quick they were, we expected them to be there or thereabouts but not that quick," he admitted.
"We need to dig into it and see if we can find a lot of extra lap time. Of course we can still turn up our engine, but we don't have six tenths of turning up our engine, you know?"
Asked if he was confident that Mercedes would find the extra time from the car to see off the Red Bull threat in Saturday's qualifying session, Rosberg sounded anything but.
"Confident after today? No, because Red Bull was quicker. But I'm really confident that we can do a great job and improve the car - if it's enough, I don't know."
"If today was qualifying they would be in front of us so we definitely need to find some more pace and it's not going to be easy," he pointed out. "We definitely have a lot of homework to do. We need to find some more performance.
"In the car I have some work to do as well, I'm not 100 per cent yet," he added. "The most important thing is just getting the car right, getting the balance right, getting good laps, getting good rhythm. Qualifying is very, very important at this race."
If he wins here this weekend it will be his forth consecutive Grand Prix victory at Monaco, a feat not achieved since Aryton Senna in the early 1990s. However, that sort of thing didn't seem to much interest Rosberg.
"That would mean not much - winning the race would mean a lot to me because that's the awesome part. It's my home, I love winning here, it's the biggest thrill, so that would mean a lot."
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