Lewis Hamilton will start the Italian Grand Prix on pole position, but his advantage could be compromised by starting on a damaged tyre.
Hamilton set the fastest time in Q2 at Monza on Saturday, but flat-spotted his front-right tyre and was unable to set a quicker lap in the session - which determines which rubber drivers will start the race with.
Leading the championship by nine points, Hamilton could apply to replace the tyre if it is seriously damaged - as he did successfully earlier this season in Baku - but his opening stint could be compromised if stewards decide safety is not an issue.
The Silver Arrows were in a class of their own at the 'Temple of Speed', easing to the top of the timesheets on harder compounds than their main rivals Ferrari and Red Bull in Q2 and Sunday will surely be a straight shootout between Hamilton and Rosberg.
Hamilton may well be on even another level to his stable-mate, clocking a fastest time of one minute, 21.135 seconds, almost half a second quicker than Rosberg, and taking top spot in every session.
The omens are strong for Hamilton, who has won from pole in each of the last two seasons - the streak of pole-sitting victories at Monza stretches back to 2010.
Behind Mercedes come Ferrari duo Sebastian Vettel and Kimi Raikkonen, with the Scuderia desperate for a strong weekend in front of their passionate fans in the midst of a dismal season so far.
A strong start could put the red cars ahead off the line, but Vettel and Raikkonen need errors from Hamilton or Rosberg if they are to have a hope of victory.
Mercedes power helped Valtteri Bottas take fifth ahead of Red Bull's Daniel Ricciardo and Max Verstappen - who should be well out of the way of Vettel and Raikkonen after their squabbles in Belgium last week.
The Mercedes-assisted Force India pair of Sergio Perez and Nico Hulkenberg are next on the grid, with Esteban Gutierrez to start 10th after taking a Haas car into Q3 for the first time in their short F1 history.
1. Lewis Hamilton (Mercedes) 1:21.135
2. Nico Rosberg (Mercedes) +0.487 seconds
3. Sebastian Vettel (Ferrari) +0.837secs
4. Kimi Raikkonen (Ferrari) +0.930secs
5. Valtteri Bottas (Williams) +1.253secs
6. Daniel Ricciardo (Red Bull) +1.254secs
7. Max Verstappen (Red Bull) +1.276secs
8. Sergio Perez (Force India) +1.679secs
9. Nico Hulkenberg (Force India) +1.701secs
10. Esteban Gutierrez (Haas) +2.049