The Mercedes of Lewis Hamilton was in a class of its own during Friday's practice sessions at the Canadian Grand Prix.
Hamilton was victorious at the Circuit Gilles Villeneuve last year and comes into this race with the wind in his sails after a successful Monaco Grand Prix last time.
The double defending world champion topped timesheets in both sessions on Friday, but the scrap behind him suggested both Saturday and Sunday could be harder to call.
Sebastian Vettel was closest to Hamilton's 1:14.212 in FP2, three tenths behind in a Ferrari that has brought turbo upgrades to Canada, in a session that saw team lay plenty of rubber down in race simulations.
Hamilton and Rosberg between them got through 83 laps, while the German put 22 laps into one pair of ultrasofts in FP1 to suggest degradation is little to worry about - especially when considering temperatures are expected to plummet on Sunday.
The supersoft tyres performed well in the cool conditions of FP1 - Hamilton beating Rosberg by over three tenths with red-walled boots on, despite his team-mate using the quickest compound.
The first session's main highlight was Felipe Massa slamming his Williams into the barriers at the first corner - the scene of his race-wrecking shunt two years ago - and ruining his back-end. His engineers deserve plenty of credit for getting the car back out for FP2, although the incident gave plenty of exposure to F1's new multi-million-dollar sponsors...
Mercedes had gone 1.5seconds quicker than any of their rivals in FP1 in 2015, but that gap had shrunk to four tenths this time around, while fourth-fastest Max Verstappen and 15th-quickest Romain Grosjean were separated by less than a second in the second run.