Reigning MotoGP champion Marc Marquez says he could not keep up his benchmark pace in pre-season testing at Sepang because he is still recovering from surgery on his left shoulder.
Marquez struggled with shoulder pain throughout his title-winning 2018 season and arrived at Sepang still recovering to full fitness after surgery last month.
Although he ended Wednesday's first day of running with the fastest time, which was more than a quarter of a second clear of second-placed Alex Rins, the Honda rider completed just 29 laps.
Marquez said he was only able to keep his pace up for two consecutive laps at most and add he is not yet fit to complete a race distance.
"To be fast on one, two laps is not a problem but to do a long run will be impossible," said Marquez.
"I'm struggling more in the change of direction from left to right, especially from Turn 5 to 6 and Turn 12 to 13 is where I'm struggling more, and then the brake points of Turn 9 and Turn 12.
"Luckily it is only the left corners, on the right corners I feel like completely normal.
"But on the other hand, I expected to be better than what I am.
"I am riding but there still remains a lot of work to do because still I don't have power.
"We stopped early today, but there still remains two days and tomorrow we will see if I get up better or worse, but basically the feeling is that I'm happy to be back on the bike."
Fellow Honda rider Cal Crutchlow is also recovering from surgery, after breaking his ankle in a crash at Phillip Island last October.
He was 14th on his return to MotoGP action at Sepang and said his initial laps on Wednesday were "horrendous".
"[It was] actually better than expected, considering I'm wearing a boot a couple of sizes oversized because I asked Alpinestars to make me that as a precaution," said Crutchlow.
"I struggled to get the rear-brake lever, because when I lift my foot, my foot comes up in the boot, and it doesn't bring the boot up. Otherwise I feel good.
"I felt horrendous the first laps of the day, on my first lap I thought I was doing a 2m01s, but I did a 2m08s.
"I'm just learning to ride again. It felt good to be able to ride again. I can be competitive this season."
Crutchlow, who was a little over a second slower than Marquez, said he could have gone faster.
"I didn't push for a lap time," he said. "I went back out at the end of the day but I had a problem, not a bike problem.
"But I felt I could have gone a significant amount faster if I needed to, which is nice because sometimes you're half a second off thinking you can't go any faster."