Mercedes boss Toto Wolff has said that a change in set-up was the reason why the team had an uncharacteristically poor showing in FP2 in Monaco.
“We took a wrong junction in setting up the car that we thought would be good," Wolff told Sky Sports F1 after the end of of Thursday's practice.
“We couldn't back out of it. We committed to the set-up. It takes a couple of hours to undo that, more than a session lasts. We decided to just push through and collect some data.
"The issue was an overall lack of grip, which drivers complained about. Not just the front but also the rear. It went out of the window everywhere.
“We were pretty competitive in the morning and so we just need to back track it. That's not a very difficult exercise.
"Nevertheless we lost a session where we could have progressed a little bit. We're lacking data.
"Now it's about sticking heads together, staying calm and trying to work as good as possible Saturday morning."
Valtteri Bottas ended the session in tenth place, and his team mate Lewis Hamilton was eighth fastest. Both were over a second slower than Ferrari's Sebastian Vettel.
"I hope that position is not real," said Bottas. "We can't be too happy with P10 and P8 as a team.
"We made some changes from practice 1 to practice 2, mechanical changes, trying to help balance in a few corners. But we went on the wrong direction in other places.
""We definitely both struggled, but we know how to fix it," he said. "We tried something at the end of the practice 2 session which was a bit better, but the tyres were old then.
"At least we have time to work things out," he added. "We have a full day tomorrow to look at everything, and we still have practice 3 before the qualifying.
"But other cars are looking good as well," he warned.
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Gallery: All the pictures from Thursday in Monaco
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