Fabio Quartararo shaded reigning MotoGP champion Marc Marquez to top Friday afternoon's second practice session for this weekend's Czech Grand Prix at Brno.
Andrea Dovizioso's benchmark time from the morning's opening practice session was immediately beaten by Suzuki rider Alex Rins, who laid down a 1m56.674s to lead the early running.
That remained the top time until Maverick Vinales posted a 1m56.084s with just over half of the 45-minute session remaining, a time that stood until Marquez went top with the first sub-1m56s lap of the day - a 1m55.825s - with six minutes left on the clock.
But with just two minutes remaining, Petronas SRT Yamaha rider Quartararo pulled out a 1m55.802s to go 0.023s faster than Honda rider Marquez.
Dovizioso had climbed to second late on in the session before being demoted to third by Quartararo, and ended up with an identical time to Ducati stablemate Jack Miller, a 1m56.071s - with the Australian credited with third place.
Behind that pair, Vinales was fifth on the best of the factory Yamahas, unable to improve on his earlier time and ending up 0.282s off the pace.
His teammate Valentino Rossi had an eventful session, suffering what appeared to be a blown engine midway through the session and cruising back to the pits with smoke pouring from his M1.
The Italian was soon back out on his second Yamaha however, and ended up ninth-fastest, behind Rins' Suzuki, Quartararo's teammate Franco Morbidelli and Cal Crutchlow (LCR Honda).
Completing the top 10 behind Rossi was Danilo Petrucci on the second factory Ducati.
Takaaki Nakagami (LCR) and Aleix Espargaro (Aprilia) both suffered crashes on their way to 12th and 15th respectively, split by top KTM rider Miguel Oliveira in 13th and Jorge Lorenzo's injury substitute at the works Honda team, Stefan Bradl, in 14th.
Suzuki wildcard Sylvain Guintoli was 17th-fastest, having been fifth in FP1 behind Oliveira.