Mercedes continued to demonstrate their dominant one-lap pace as Nico Rosberg and teammate Lewis Hamilton headed the field ahead of qualifying for the prestigious Monaco Grand Prix. Rosberg, who has claimed pole position in the past two races, was 0.318 seconds quicker than Hamilton, who started on pole in China last month, in Thursday’s second practice session. The best of the rest were Ferrari, with Fernando Alonso third quickest ahead of his teammate Felipe Massa. Next came the Red Bull of Mark Webber and Kimi Raikkonen, while the Finn’s Lotus teammate, Romain Grosjean, fared less well as he clattered into the wall at Sainte Devote and lost vital running time.

It was another good day for Mercedes, but the challenge now is to turn their single-lap pace into competing over the length of a grueling race. Despite their practice and qualifying prowess, Mercedes have yet to record a win so far in 2013, securing just two podiums.

“It seems that we are quick again on one lap but we have been working hard again to make improvements to our race pace,” Rosberg said, according to the official Formula One website. “It will be interesting to see where we are compared to the others over the weekend as it's not really representative today.”

Alonso, who won his home Grand Prix in Spain two weeks ago to close the gap on Sebastian Vettel and Raikkonen ahead of him in the drivers’ championship standings, does not believe much can be read into the practice times on the famous street circuit in the principality.

“Even if the feelings are positive and we got through the day without any problems whatsoever, we still don’t have a clear idea of the pecking order in the field,” he explained. “We will have to wait a bit to see where all our rivals really are, because here too, until Saturday, no one pushes a hundred percent: the barriers constitute too high a threat to take risks in the first free practice sessions.”

Vettel only managed the ninth fastest time as his car was worked on during the session. “Unfortunately we lost quite a lot of time in the afternoon while we were making some changes, but that can happen on Friday, or in this case Thursday,” he said. “We’d like to be a little bit more competitive, so we need to try and find some more lap time.”

The three-time champion has been the leading critic of this season’s tires, which have suffered heavy degradation through the season and reached a nadir in Barcelona when there were a slew of pit stops. But, while the manufacturer Pirelli will make some modifications from the Canadian Grand Prix onwards, there will not be sweeping changes due to the protests from Lotus and Ferrari.

Thursday was another largely disappointing day for both McLaren and Williams, although Jenson Button is more encouraged by the McLaren’s progress. “Our pace on a long run looks surprisingly good, although we’re not quite there with our qualifying pace yet,” he said. “Still, I feel happier with the car here than I have the past few weekends.”

Where to watch: Qualifying for the Monaco Grand Prix will get underway at 8 a.m. on Saturday. Coverage will be provided by the NBC Sports Network, with a live stream available on NBC Sports Live Extra