Defending Catalunya MotoGP winner Jorge Lorenzo
lead a top three covered by just 0.070s during Fridays opening free practice for the 2013 event.
Lorenzo, who won last year's race by five seconds from Dani Pedrosa, outpaced the Repsol Honda title leader by 0.023s this morning with a best time of 1m 42.442s set shortly after the halfway mark.
That lap time compares with Pedrosa's race lap record of 1m 42.358s, set on his way to victory in the 2008 grand prix.
Completing the close top three was Monster Yamaha Tech 3 star Cal Crutchlow, who will be seeking his third podium in a row in Sunday's race.
Lorenzo's Factory Yamaha team-mate Valentino Rossi
made a brief appearance at the top during the opening minutes of a bright and sunny session on his way to fourth place (+0.469s).
Andrea Dovizioso was the leading Ducati rider in fifth (+0.689s), while Alvaro Bautista lowsided from his Gresini Honda in the closing stages on his way to sixth (+0.690s).
Stefan Bradl (LCR Honda), Nicky Hayden
(Ducati), Marc Marquez (Repsol Honda) and Aleix Espargaro (Aspar) completed a top ten covered by 1.392s.
Pramac Ducati's Andrea Iannone was one of numerous riders to take a detour through the gravel. Fellow rookie Bradley Smith, riding with an injured hand from Mugello, began the weekend in twelfth for Tech 3 Yamaha.
Pramac's Ben Spies continues to be side-lined by his healing shoulder and is being replaced by Ducati test rider Michele Pirro. Pirro, starting his fourth race of the season, was 13th quickest this morning.Free practice 1:
1. Jorge Lorenzo
2. Dani Pedrosa
3. Cal Crutchlow
4. Valentino Rossi
5. Andrea Dovizioso
6. Alvaro Bautista
7. Stefan Bradl
8. Nicky Hayden
9. Marc Marquez
10. Aleix Espargaro
11. Andrea Iannone
12. Bradley Smith
13. Michele Pirro
14. Randy De Puniet
15. Colin Edwards
16. Karel Abraham
17. Danilo Petrucci
18. Hector Barbera
19. Yonny Hernandez
20. Hiroshi Aoyama
21. Claudio Corti
22. Michael Laverty
23. Bryan Staring
24. Lukas Pesek