Nico Rosberg highlighted Mercedes GP's position as a dark horse for this weekend's Canadian Grand Prix, topping the times in the opening practice session on Friday.
But the big news of the first day of action was Sebastian Vettel's crash, the Red Bull driver starting his weekend on the back foot after a costly driving mistake.
The session had to be red-flagged with around 33 minutes to go when Vettel crashed into the "Wall of Champions" after his car jumped over the kerb at the final corner.
The right side of the Red Bull car was heavily damaged and the world champion, who had managed just eight laps before that, was unable to return to action.
Rosberg, meanwhile, enjoyed a trouble-free day to finish ahead of Ferrari's Fernando Alonso and his own Mercedes team-mate Michael Schumacher.
Felipe Massa was fourth fastest, with Jenson Button completing the top five ahead of McLaren team-mate Lewis Hamilton.
With the teams testing new parts, and with the track very dirty at the start of the session, it took several minutes before a time was set, with Toro Rosso's reserve Daniel Ricciardo becoming the first driver to complete a full lap over 20 minutes after the start.
Alonso quickly removed the Australian from the top spot, the Ferrari driver going four seconds quicker despite a scare at the exit of the hairpin. His time of 1m22.1s was bettered on the next lap, the Spaniard lapping in the 1m19s before heading back to the pits.
Schumacher took to the top with less than an hour left, the Mercedes driver going over a second faster than Alonso, with Hamilton and Jaime Alguersuari also setting fast times to relegate Alonso down to fourth.
Hamilton was next to move to the top with a time of 1m18.395s, a benchmark that lasted until Massa moved into the 1m17s with some 45 minutes of the session left.
Once the session was restarted following Vettel's accident, it was Alonso who returned to the top of the times with a lap of 1m17.102s, relegating his team-mate to second. The Spaniard went even quicker moments later, by a full second, to become the first man to lap in the 1m16s.
With 13 minutes to go, Rosberg jumped to first place, outpacing Alonso by over a tenth of a second on his 28th lap of the day. The Mercedes driver stayed on track for several minutes and posted a 1m15.591s with seven minutes remaining.
Renault's Vitaly Petrov was one a few drivers with problems, the Russian not managing to set a time until there were less than 10 minutes of the session left.
Pos Driver Team Time Laps 1. Nico Rosberg Mercedes 1m15.591s 32
2. Fernando Alonso Ferrari 1m16.139s + 0.548 27
3. Michael Schumacher Mercedes 1m16.549s + 0.958 30
4. Felipe Massa Ferrari 1m16.658s + 1.067 26
5. Jenson Button McLaren-Mercedes 1m16.676s + 1.085 20
6. Lewis Hamilton McLaren-Mercedes 1m16.842s + 1.251 19
7. Rubens Barrichello Williams-Cosworth 1m16.990s + 1.399 28
8. Paul di Resta Force India-Mercedes 1m17.294s + 1.703 26
9. Nick Heidfeld Renault 1m17.445s + 1.854 28
10. Nico Hulkenberg Force India-Mercedes 1m17.549s + 1.958 20
11. Sergio Perez Sauber-Ferrari 1m17.662s + 2.071 27
12. Mark Webber Red Bull-Renault 1m17.820s + 2.229 30
13. Jaime Alguersuari Toro Rosso-Ferrari 1m18.458s + 2.867 31
14. Vitaly Petrov Renault 1m18.506s + 2.915 15
15. Daniel Ricciardo Toro Rosso-Ferrari 1m18.648s + 3.057 35
16. Sebastian Vettel Red Bull-Renault 1m18.852s + 3.261 8
17. Pastor Maldonado Williams-Cosworth 1m18.932s + 3.341 20
18. Jarno Trulli Lotus-Renault 1m19.274s + 3.683 29
19. Heikki Kovalainen Lotus-Renault 1m19.422s + 3.831 30
20. Kamui Kobayashi Sauber-Ferrari 1m19.577s + 3.986 26
21. Jerome D'Ambrosio Virgin-Cosworth 1m19.838s + 4.247 31
22. Tonio Liuzzi HRT-Cosworth 1m19.960s + 4.369 23
23. Timo Glock Virgin-Cosworth 1m20.520s + 4.929 21
24. Narain Karthikeyan HRT-Cosworth 1m20.839s + 5.248 27 All Timing Unofficial