Jorge Lorenzo found the going tough as the Yamaha Factory Racing star began his 2014 MotoGP testing programme at Sepang.
Lorenzo isn't quite feeling at home on the M1 after changes to the electronics as a result of the new 20-litre fuel allowance affected the Yamaha's performance.
“As always it's difficult to come back again in a good shape after the Winter, some months without training changes you a lot so the first day is always tough. The bike has changed quite a bit compared to last year,” he said.
“I didn't do more than three laps in a row; I need to get more used to this bike and get more physical condition.
“Today has been especially hard because of the new regulation of 20 litres [of fuel]. We had to modify something in the electronics and in the new engine to [enable us] to finish a race with 20 litres," Lorenzo added.
“This has created a problem in the entry of the corner and the middle of the corner, because the bike is a little more nervous. It's difficult because you are using more tyre during the laps.
“Tomorrow our target is to make the bike more easier to ride like last year and we are working in that way. We are also working on the gearbox and the clutch but the bike now is nervous with the 20 litre regulation and I'm not very happy about that."
Lorenzo was fourth fastest overall with a best lap of 2m 01.082s, which left him 0.796s off the pace of Repsol Honda's Marc Marquez.
He briefly slotted into second position before being shuffled back to fourth in the closing stages by team-mate Valentino Rossi and Honda's Dani Pedrosa.