Lorenzo set the pace with a lap time of 1:48.375, beating teammate and multiple Mugello winner Rossi by just 34 thousandths of a second.
Tech 3’s Cal Crutchlow was third from Ducati Team’s Nicky Hayden and Repsol Honda’s championship-leading Dani Pedrosa, who is aiming for a hat-trick of 2013 victories this weekend.
“In the morning it was wet and bad conditions so we preferred to not exit at the end of FP1 with the slick tires as we thought the track was dangerous,” Lorenzo said. “We had to wait for the afternoon and dry conditions.
“From the beginning the Yamaha riders were very strong and competitive which means the track is working well for us this year. We have to wait for the improvement of our rivals and the possible change in weather that can change our performance but for the moment we are very competitive and happy.”
Marquez had led a topsy-turvy opening practice in the morning, but for a currently unknown reason lost control of his bike in the afternoon session. Having slid down the grass verge towards Turn 1, the 20-year-old was treated in the circuit Medical Centre but was confirmed to have escaped serious injury. Monster Yamaha Tech 3’s Bradley Smith also crashed, landing on his left arm at Turn 7.
"Just after the hill on the straight, I grabbed for the brakes but I (lost) the front," he explained later in the afternoon, having missed the usual post-session press call. "I tried to save it but the bike was pulling me towards the wall, so I jumped from the bike to avoid hitting it. I hit my chin hard and strained my neck quite badly; I also have some contusions to my right shoulder, arm and leg, but other than that I'm okay. Thanks to all the medical team that were quickly on the scene to assist me. Now I need to rest and see how I feel later tonight and in the morning."
"Bearing in mind the crash he had, he is okay," Team Principal Livio Suppo told motogp.com. "His chin was very swollen but, considering the speed, he has been very lucky…he jumped off the bike to avoid the wall, but the crash was really big.
"In theory there is nothing broken, so it should be possible, but for sure it is better to wait until tomorrow morning to see how he feels."
The top 10 was rounded out by Energy T.I. Pramac Racing’s Andrea Iannone in sixth position, Ducati’s Andrea Dovizioso who rode with neck pain following a morning crash, LCR Honda MotoGP’s Stefan Bradl, Power Electronics Aspar’s Randy de Puniet (the leading CRT runner) and Ducati Test Team’s wildcard entry Michele Pirro, riding the GP13 Lab bike as he also did in Jerez.
The third and final practice period, which is the final session to have a bearing on the Q2 Qualifying order, will begin on Saturday at 9:55am local time.
Jerez race winner Esteve Rabat jumped in front of Simone Corsi to lead the second Moto2™ practice session at Mugello on Friday. The Tuenti HP 40 and NGM Mobile Racing riders were joined in the top three by Italtrans Racing Team’s Takaaki Nakagami.
Rabat reduced the weekend’s best time to 1:53.583 as clouds blew over to reveal sunshine. With Corsi the leading Italian rider and Nakagami dropping to third from the top spot in the morning, Johann Zarco and Xavier Simeon completed the top five for Came Iodaracing Project and Desguaces La Torre Maptaq, respectively.
Alex de Angelis was sixth on the NGM Mobile Forward Racing machine, edging championship leader Scott Redding (Marc VDS Racing Team) into seventh spot.
Red Bull KTM Ajo’s Luis Salom set the Moto3 pace. The Spaniard and championship-leading compatriot Maverick Viñales were the only riders to duck inside the two-minute lap time barrier, as morning pace-setter Jonas Folger completed the top three at Mugello.
The heavy rain of Thursday had been replaced by bright sunshine by the time Friday afternoon arrived, allowing Salom to pip Viñales by 25 thousandths of a second thanks to his best effort of 1:59.606.