Nicky Hayden set the MotoGP pace during day one of private testing at Jerez, but was behind two World Superbike riders on the timesheets.
Hayden set a best of 1m 40.855s while evaluating chassis and swingarm developments for his factory Ducati.
But it was Aprilia WSBK rider Eugene Laverty who led the way with a 1m 40.185s Wednesday best, followed by Kawasaki ZX-10R star Tom Sykes on a 1m 40.400s.
Laverty - whose brother Michael is listed on the 2013 MotoGP entry list with PBM - is thought to have used a soft tyre to set his pace-setting lap.
UPDATE: Laverty has now confirmed on Twitter (@EugeneLaverty) that he set his best time with a qualifying tyre, but
also that he recorded a 1m 40.4s on a race tyre.
"Added bonus of lapping faster than Ducati MotoGP today at Jerez. The Aprilia RSV4 is one great little bike!" he wrote.
Laverty thus matched Sykes on the race tyre, the Englishman setting his best lap time 'on a race tyre during the final morning'.
"I did a 1m 40.4 on an SC1 tyre and although we went to try an SC0 [qualifying] tyre at the end of the day, with the low sun and so on, I thought we would give it a miss," Sykes explained.
Sykes had been credited as quickest with low 1m 41s laps on the previous two days of testing. The Jerez MotoGP race lap record is a 1m 39.731s. Next season will see Jerez host a WSBK event for the first time since 1990.
While Hayden got down to work in Ducati's final test of 2012, new team-mate Andrea Dovizioso
completed just two laps.
The Italian, due to have a plate removed from his shoulder in early December, was halted by an unrelated neck issue and was forced to miss the rest of the day. The top 2012 satellite rider hopes to be fit for action on Thursday.
In Dovizioso's absence, new factory test rider Michele Pirro - again standing in for the injured Ben Spies - was next best of the grand prix riders with a 1m 41.720s, followed by Pramac Ducati rookie Andrea Iannone on a 1m 41.834s.
Avintia Blusens CRT riders Hiroshi Aoyama and Hector Barbera recorded best laps of 1m 42.5s and 1m 42.9s respectively.
MotoGP testing at Jerez continues on Thursday and Friday, alongside the Ducati and BMW WSBK teams. Aprilia and Kawasaki concluded their test on Wednesday evening.CLICK HERE
for pictures from the test.