Nico Rosberg says F1's reduced downforce was noticeable at Spa on Friday as his W04 lacked the cornering speed of its predecessor.
Ahead of this weekend's Belgian Grand Prix, several drivers spoke about how the rules reducing downforce would have an impact on their performances, highlighting a belief that they would not be able to take Eau Rouge flat-out.
And although Mercedes had the beating of their rivals on Friday, even Rosberg says the lack of downforce was evident.
"We are actually slower this year in the corners than last year - last year we had more grip so the corners felt better," he told ESPNF1.
"But," he added, "relative to the others I'm sure our car feels great here and we're going strong here today.
"Today went according to plan, it was OK.
"It's difficult here because to be quick here you have to run less downforce to be quick on the straights , which means our car is sliding more in the corners and that means it's more difficult to drive and a bit unusual - less grip in general.
"It takes a bit of adapting and finding the right set up, but all in all we are going in the right direction."
The German finished Friday's second practice with a 1:49.793, which put him 0.604s down on his team-mate Lewis Hamilton. Their closest rival, Fernando Alonso, was 0.741s slower than the Brit.
However, Rosberg isn't sure whether Alonso will remain Mercedes' closest challenger.
"I'm not really sure yet," he said when asked about Mercedes' rivals. "It's a bit of a mixture.
"All of a sudden the Red Bulls are quick on the straights in some circumstances which is awkward, so it will be an interesting evening trying to analyse everything and try to nail it for tomorrow, and also getting the compromise right between qualifying and the race."