Nine-time world champion Valentino Rossi found a late fast lap to set the quickest time in practice for Sunday's Catalunya grand prix in Barcelona.
Rossi, 34, has won at the Barcelona circuit nine times throughout his career and pipped Yamaha team-mate Jorge Lorenzo with two minutes left.
Championship leader Dani Pedrosa set the third best time of the afternoon, with Alvaro Bautista in fourth.
British rider Cal Crutchlow was fifth ahead of rookie Marc Marquez.
Rossi was second on his return to Yamaha in the opening race of the season in Qatar in April, but has struggled since, and is currently only sixth in the world championship standings.
He spent most of the afternoon session outside of the top six but came up with a lap of one minute 42.297 seconds - inside the lap record - to take top spot.
Crutchlow's team-mate and fellow Briton Bradley Smith ended the day in 14th place after another high-speed crash.
Smith, 22, and was left limping away after another incident as he crashed at Turn Three.
Smith said: "I am lucky I didn't damage my body in the crash because it was another big fall.
"I lost the front and as I tried to save it the rear tyre gripped and threw me off. The bike hit my left knee and that's why I was limping in the gravel but luckily I am fine."
Catalunya practice times:
1. Valentino Rossi (Ita) Yamaha 1'42.297
2, Jorge Lorenzo (Spa) Yamaha 1'42.346
3. Dani Pedrosa (Spa) Repsol Honda 1'42.557
4. Alvaro Bautista (Spa) Gresini Honda 1'42.752
5. Cal Crutchlow (GB) Tech 3 Yamaha 1'42.776
6. Marc Marquez (Spa) Repsol Honda 1'42.857
7. Nicky Hayden (USA) Ducati 1'42.890
8. Andrea Dovizioso (Ita) Ducati 1'42.988
9. Stefan Bradl (Ger) LCR Honda 1'43.005
10. Aleix Espargaro (Spa) Aspar ART 1'43.204