Lewis Hamilton was at a loss to explain where Mercedes' pace had disappeared to after being cast a second adrift in second practice for the Azerbaijan Grand Prix.
Mercedes was plagued by tyre warm-up issues at the Monaco GP but it appears the team has failed to find a fix, potentially even taking a step in the wrong direction.
"Pace-wise we've not gone anywhere forwards," said Hamilton after registering only the 11th fastest time. "If anything, it looks like we've gone backwards but I don't really know."
Hamilton's best lap was a one minute 43.156secs, just over a second off the session-topping pace of Red Bull driver Sergio Perez.
Despite the pace deficit, however, Hamilton felt he had enjoyed a "really good day" in the car, adding that "it was clean, I got all the laps that were needed, there was not really any mistakes, I had one lock-up in P1", but "we were just slow".
"In general, I feel like I'm driving well," assessed Hamilton. "The car felt better in P1, there was just no more time in it.
"We're definitely quite a chunk down and everyone will be scratching their heads trying to figure it out, looking into the data trying to figure out how we can improve."
The Mercedes W12 is "limited"
After claiming three wins from the first four races this year, Hamilton lost the championship lead to Red Bull rival Max Verstappen after finishing a disappointing seventh in Monaco.
Although happy with the balance of his car in the first session of the day, Hamilton said of FP2: "It didn't feel good.
"Just in general, I was pushing upwards on the limit but the car is limited. There are areas that I should just be quicker but there is no more grip.
"We'll work at it. It's not easy to be out of the top 10 on pace when we've had pace in other places but I don't really know why we are where we are."
As for his chances in Sunday's race, Hamilton commented: "I think it's impossible to say at the moment."
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