Marco Simoncelli set the pace in the opening practice session for the Italian Grand Prix at Mugello on Friday.
The Italian Gresini rider posted a time of 1m48.987s in the dying moments of the session to outpace championship leader Casey Stoner by 0.040sec.
Andrea Dovizioso made it three Hondas in the top three, with world champion Jorge Lorenzo the first non-Honda rider in fourth position on the Yamaha.
Teammate Ben Spies, the winner of the previous race in Assen, completed the top five.
Local hero Valentino Rossi started his weekend on the back foot after his Ducati broke down with some 17 minutes of the session left, the Italian having to switch to his spare bike for the remainder of the session.
Minutes later, the Italian returned to the pits and was seen pushing the second bike down the pit lane. He finished down in 13th.
Dani Pedrosa made his return to action following his injury, having missed the last three races, and the Spaniard enjoyed a positive session, finishing in seventh position.
On a sunny day at the Italian track, Nicky Hayden was the early pace-setter before he was quickly relegated by Simoncelli, who jumped to the top of the times as he continued to show his strong form as of late.
Stoner moved to first place with 22 minutes left, becoming the first man to lap in the 1m49s. Simoncelli improved his lap time right after the Australian, but his time was only good enough for second, even though he was also in the 1m49s.
Both men improved their times on their following laps, with Stoner stopping the clock at 1m49.027s. Lorenzo then jumped up to second with less than 10 minutes to go, but was relegated to third by Dovizioso by two minutes left.
Simoncelli was the only man to lap in the 1m48s, the Italian going quickest when the clock was already at zero.
The field is down to 16 bikes this weekend after Pramac's Loris Capirossi was unable to ride because of his injury following a crash in the Dutch TT.
The team is expected to test Frenchman Sylvain Guintoli on Monday to assess him as a possible replacement in case the Italian can't race in the next event.
Pos Rider Team Time Laps
1. Marco Simoncelli San Carlo Honda Gresini 1m48.987s 21
2. Casey Stoner Repsol Honda Team 1m49.027s + 0.040 16
3. Andrea Dovizioso Repsol Honda Team 1m49.088s + 0.101 21
4. Jorge Lorenzo Yamaha Factory Racing 1m49.251s + 0.264 20
5. Ben Spies Yamaha Factory Racing 1m49.364s + 0.377 20
6. Colin Edwards Monster Yamaha Tech 3 1m49.810s + 0.823 19
7. Dani Pedrosa Repsol Honda Team 1m50.104s + 1.117 19
8. Nicky Hayden Ducati Team 1m50.203s + 1.216 19
9. Hiroshi Aoyama San Carlo Honda Gresini 1m50.629s + 1.642 21
10. Alvaro Bautista Rizla Suzuki MotoGP 1m50.658s + 1.671 16
11. Cal Crutchlow Monster Yamaha Tech 3 1m50.683s + 1.696 19
12. Randy De Puniet Pramac Racing Team 1m50.729s + 1.742 19
13. Valentino Rossi Ducati Team 1m50.780s + 1.793 13
14. Hector Barbera Mapfre Aspar Team MotoGP 1m51.153s + 2.166 18
15. Toni Elias LCR Honda MotoGP 1m51.868s + 2.881 19
16. Karel Abraham Cardion AB Motoracing 1m51.876s + 2.889 18