Valentino Rossi insisted different track conditions at Sepang made comparisons between the latest Ducati GP11.1 and the original GP11 used in February's pre-season tests 'difficult'.
During the five days of testing - Rossi missed one day due to sickness - the Italian had been between 1.012sec and 1.804sec behind the fastest rider (putting him between 9th and 13th on the timesheets).
With the best lap times often set in the opening hour of testing, before the intense heat grilled the circuit, that time gap was widely considered to look worse that it actually was - Rossi not electing to push hard for an early lap. Rossi was also still struggling for strength in his healing shoulder.
But after the first day of the Malaysian Grand Prix, and now using an aluminium front section on the GP11.1, Rossi was left in 13th place, 2.427sec from pace setter Dani Pedrosa.
Despite the conditions, Pedrosa's best lap time was almost one-second under the official lap record, although over one-second behind the best test lap of 1min 59.665sec, set by his Repsol Honda team-mate Casey Stoner.
Rossi was the slowest of the five Ducati riders on Friday, with the top Desmosedici - the GP11 of Pramac's Randy de Puniet - 1.909sec behind Pedrosa.
“The track conditions are very different, worse actually, than when we tested here during the winter, because the asphalt was very slippery today," said Rossi. "It was really bad this morning, just a bit better in the afternoon.
"That makes it difficult to make a comparison between then and today, but we certainly weren't as fast as we'd like to be.
"We changed something with the rear suspension at the end of the session that helped to improve the feeling with the bike, but we haven't made enough progress in terms of lap times. Tomorrow we'll see if we're able to do better with a bit more grip.
"It wasn't bad under braking today, but I'm not able to be fast in the corners, especially the fast ones. I really hope to be able to use the hard tyres because that would be the right choice for the race.”