Lewis Hamilton's belief that Red Bull and Ferrari would continue to be threats at the Canadian Grand Prix was borne out when the Briton slipped behind the leading contender from both McLaren's main rivals in the third and final free practice session at the Circuit Gilles Villeneuve.
Although he briefly featured at the top of the timesheets himself, Hamilton ultimately had to settle for third overall as both Sebastian Vettel and Fernando Alonso usurped him in the second half of the session. Hamilton returned the favour after bolting on the supersoft Pirellis, but Vettel wasted little time in putting Red Bull back on top, despite using the harder tyre. Alonso's first run on the red-rimmed rubber then allowed him to take another turn in P1, knocking a couple of tenths from Vettel's benchmark, but the defending world champion was not to be outdone and returned to the fray in the closing moments to reassert himself - and an RB8 forced to make two design changes in a week -with a time of 1min 14.442secs - just a whisker inside Alonso's best.
Hamilton was two-tenths off the pace but, with the top ten all recording laps in the 1min 14s and the last of those just half a second back from Vettel, the stage appears set for another tense qualifying session. Mark Webber, Pastor Maldonado, Felipe Massa, Michael Schumacher, Romain Grosjean, Kimi Raikkonen and Nico Hulkenberg completed the top group, with the latter's Force India team-mate, Paul di Resta, and the two Saubers also in contention. A little further back, Bruno Senna and Jenson Button - the Briton again complaining about an indifferent front end to his McLaren - were the last to get to within a second of the pace, while the second Mercedes of Nico Rosberg should also be considered a top ten contender despite a fuel flow issue seeing him grind to a halt with just an installation lap to his name.
The German was not the only one to languish at the bottom of the timesheets with nothing to show for his, admittedly brief, efforts, as Toro Rosso's Jean-Eric Vergne was also left without a time after losing his STR7 at the entry to the opening corner and, after clipping the grass between turns one and two as he fought to correct, was left powerless to prevent a meeting with the barriers.
Their absence allowed Vitaly Petrov to claim 17th spot, two behind Button, but now behind the other Toro Rosso of Daniel Ricciardo. Heikki Kovalainen continued to make up for the time he lost on Friday morning to put over a second between the Caterhams and HRT, for whom Pedro de la Rosa again showed strongly, even though the lead Marussia of Timo Glock was closer to the Spaniard then in earlier sessions.