Monaco - Jenson Button posted the fastest time in a rainy second practice at the Monaco Grand Prix on Thursday, with French rookie Romain Grosjean again impressing for Lotus and Felipe Massa finding some much-needed form.
With the track slippery after a downpour briefly interrupted the second session, drivers switched to intermediate tires. But Button had already clocked 1 minute, 15.746 seconds for McLaren on dry tires and that marker was never going to be beaten in the rain.
Grosjean, who was also second in the morning's first practice session, had a time of 1:16.138.
Massa, meanwhile, has only picked up two points from the first five races this season, and the Brazilian will be boosted by his time of 1:16.602. He was third fastest ahead of Ferrari teammate Fernando Alonso, who was quickest in the sunny morning session.
Two-time defending Formula One champion Sebastian Vettel was 10th fastest after finishing ninth in the morning.
Grosjean's confidence will be high heading into Saturday's third practice session and qualifying. The 26-year-old has made an impressive start to his F1 career - he already has a podium after finishing third in Bahrain and was fourth in Barcelona.
"The car is going well at the moment," he said. "It is important to have a car you are confident in."
In the morning session, Alonso drove smoothly to clock 1:16.265 - nearly a second faster than championship co-leader Vettel, who is tied on 61 points with Alonso in a championship race that is much closer than last year's.
Sauber's Sergio Perez was third in the morning in 1:16.711, but the Mexican was 15th quickest time in practice two.
British driver Lewis Hamilton, still seeking his first win of the season, was fourth in the morning and 11th in the afternoon.
"Hopefully Saturday will be a bit better," he said.
It proved to be a bad day for Caterham driver Heikki Kovalainen. The Finn blew his engine in the morning and swerved off the track in the afternoon at the Mirabeau turn, one of several drivers to experience difficulties there.
Brazilian driver Bruno Senna and Venezuelan Pastor Maldonadao were also troubled by Mirebeau. So was Massa, but he managed to keep things under control.
Former champions Kimi Raikkonen and Michael Schumacher struggled in the morning run, which was cut short by about 10 minutes after Kovalainen's engine sent smoke billowing through the tunnel section.
Raikkonen was hampered by suspension problems on his Lotus and failed to post a time after managing only one lap, while the front wing of Schumacher's Mercedes was dented as he flew into a chicane.
Schumacher improved to ninth fastest in the afternoon, but the seven-time former champion has had a miserable season so far, and has a five-place grid penalty in Monaco.
Monaco Formula One Grand Prix second free practice times:
1. Jenson Button (GBR) McLaren Mercedes 1:15.746, 2. Romain Grosjean (FRA) Lotus 1:16.138, 3. Felipe Massa (BRA) Scuderia Ferrari 1:16.602, 4. Fernando Alonso (ESP) Scuderia Ferrari 1:16.661, 5. Pastor Maldonado (VEN) Williams 1:16.820, 6. Nico Rosberg (GER) Mercedes AMG 1:17.021, 7. Mark Webber (AUS) Red Bull Racing 1:17.148, 8. Kamui Kobayashi (JPN) Sauber 1:17.153, 9. Michael Schumacher (GER) Mercedes AMG 1:17.293
10. Sebastian Vettel (GER) Red Bull Racing 1:17.303, 11. Lewis Hamilton (GBR) McLaren Mercedes 1:17.375, 12. Paul di Resta (GBR) Force India 1:17.395, 13. Bruno Senna (BRA) Williams 1:17.655, 14. Nico Hlkenberg (GER) Force India 1:17.800, 15. Sergio Perez (MEX) Sauber 1:18.251, 16. Vitaly Petrov (RUS) Caterham 1:18.440, 17. Jean-Eric Vergne (FRA) Scuderia Toro Rosso 1:18.522, 18. Daniel Ricciardo (AUS) Scuderia Toro Rosso 1:18.808, 19. Kimi Raikkonen (FIN) Lotus 1:19.267, 20. Timo Glock (GER) Marussia 1:19.309
21. Heikki Kovalainen (FIN) Caterham 1:20.029, 22. Charles Pic (FRA) Marussia 1:20.240, 23. Pedro de la Rosa (ESP) HRT 1:20.631, 24. Narain Karthikeyan (IND) HRT 1:20.886