Carlos Sainz has conceded to being surprised at "how rough" his Ferrari felt during practice for the Singapore Grand Prix despite topping the second session.
The Spanish driver set the benchmark time with a lap of one minute 42.587secs to finish 0.208s clear of team-mate Charles Leclerc, with Red Bull's Max Verstappen only fourth quickest following set-up issues.
The day, however, was not all smooth sailing for Sainz after initially ending FP1 over a second off the pace set by Mercedes' Lewis Hamilton, who was quickest at the end of a practice session for the first time this year.
“We faced some challenges," said Sainz. "FP1 was definitely a surprise with how bumpy and how poor the car was in general in terms of ride and how rough it felt out there.
“For FP2, we managed to improve the car but we still have some things to look at because it looks like it’s going to be a tight battle for [the top] six.
“Overall, I was feeling more comfortable in FP2 but still not quite where I wanted it to be.
"You need to have a lot of confidence to be able to put a good lap together around here and to put all of the sectors together, all of the corners together as there are a lot of them  and we are not at that level yet."
Sainz "fighting" Ferrari
Sainz twice came close to disaster in FP1, losing the rear at turn five and later at the final corner. On both occasions, the Ferrari driver narrowly avoided contact with the wall.
But when pushing during a qualifying simulation in the second outing, the Spaniard was among a number of drivers to graze the concrete on the exit of turn 19.
“It just proves that when you have moments on Friday, even if I wasn’t pushing flat out, the car and myself were still fighting each other a bit," reflected Sainz.
"I have margin in terms of the level of pushing but the more confidence I have in the car, the closer I could get to those walls."
Leclerc's "difficult day"
Leclerc may have ended Friday second fastest but that result puts a shine on an otherwise disappointing day.
The Monégasque lost significant track time in both sessions with a brake problem in FP1 and his car requiring laser scanning for an unspecified problem in FP2.
"In terms of performance, it has been a positive day," said Leclerc. "In terms of running, it has been a very difficult day for us
"We have had quite a few problems and very limited running, so we need to catch up in FP3.
"But it seems like the performance is good, so that is a good thing. But we still need to make a step for tomorrow to be ready for qualifying."