Ferrari beware, Valtteri Bottas is confident there is plenty more to come from Mercedes as they roll out a host of new upgrades for the Spanish Grand Prix.
After dominating the opening three races of 2017, Mercedes were initially forced onto the back foot in Sochi as Sebastian Vettel took pole ahead of Ferrari team-mate Kimi Raikkonen.
He failed to convert it into a race win, though, as Bottas got a sensational start in Russia on his way to a maiden race victory - a win that puts him firmly in the drivers' championship title race.
Having given up some of their speed to Ferrari last time out, Mercedes - like all the teams - have made a number of changes to their W08, including a new nose design.
Bottas is confident that can reassert Mercedes' dominance in a race that has seen a different winner each year since 2007.
"This year it is not easy, as it is a tight battle against Ferrari and it is all about the details," he told the official F1 website. "Every single bit counts.
"So there is a lot of work going into that, but also bringing new bits to the car and putting everything together. There are still quite a few more things to unlock with the package that we have.
"We feel that we have a strong car and there is potential and room for improvement in all areas to have an even stronger car."
WHAT WE LEARNED FROM PRACTICE
Mercedes' upgrade has ensured their place at the top of the timesheets heading into qualifying, with Ferrari struggling to match the pace they showed in Russia.
The Mercedes pair of Hamilton and Bottas were clear at the top of both FP1 and FP2, although their advantage was cut in the latter session.
Ferrari found themselves nine tenths adrift after the opening run in Barcelona, but that was cut to just three later in the day - however usurping the Silver Arrows proved impossible.
"Today I wasn't very happy with the feeling I was getting but I can also feel the car was quick," said Vettel following FP2. "The car was slippery but I think that was because of the conditions. I don't know who brought the most updates but it's about who brought the best."
Red Bull's hopes of being more competitive with their new upgrade came true as Max Verstappen finished just two tenths behind Sebastian Vettel, while Daniel Ricciardo was also in close attention.
Things were not so positive for Fernando Alonso, though, as he was beset by reliability issues in FP1. After a game of tennis and some work from his mechanics he was able to get 21 laps under his belt, however he remained dead last going into the weekend.
1. Sebastian Vettel (Ferrari) - 86 points
2. Lewis Hamilton (Mercedes) - 73 points
3. Valtteri Bottas (Mercedes) - 63 points
4. Kimi Raikkonen (Ferrari) - 49 points
5. Max Verstappen (Red Bull) - 35 points
1. Mercedes - 136 points
2. Ferrari - 135 points
3. Red Bull - 57 points
4. Force India - 31 points
5. Williams - 18 points
2016: Max Verstappen
2015: Nico Rosberg
2014: Lewis Hamilton
The threat of thunderstorms for qualifying on Saturday could lead to a few surprises on the grid, but they are expected to clear for the race, which is expected to be sunny and dry - similar to Friday's practice conditions.