Movistar Yamaha rider Jorge Lorenzo admitted that he was surprised to record the fastest time in both practice sessions at Motegi on Friday.
However, the two-time MotoGP champion pointed out that he could have been a lot faster had it not been for his shoulder injury, which he sustained in a mini-bike accident last Saturday.
"It was surprising how fast I was today, because the shoulder really is not the same as normal," Lorenzo told reporters. "But it seems like the bike is working very well and this is a track where in normal conditions I could probably make the biggest advantage over my rivals.
"But even with this injury I am very fast and very consistent. I believe that with normal physical conditions I could have been even faster, but there's no point in thinking about what could have happened."
The 28-year-old Spaniard added that he didn't want to do too many laps on Friday as he wants to give his shoulder adequate time to recover.
"I tried to save a little energy today and didn't do too may laps to try to save the shoulder a bit for tomorrow," he said. "From one side every day is better, from the other side each day you are doing exercise which probably doesn't help the shoulder recover. Overall I think the shoulder will be the same or a little bit better tomorrow."
Lorenzo also conceded that he didn't expect to be as competitive as he was during the first two practice sessions. The Movistar Yamaha rider finished 0.128s ahead of Repsol Honda rider Dani Pedrosa and 0.823s clear of team-mate Valentino Rossi, who is 14 points ahead of him on the MotoGP standings.
"I didn't expect to be so competitive, especially in the morning," Lorenzo said. "I expected to improve little by little, but starting from the first run I was the fastest rider and I improved even more on the last outing, so I finished first in the morning and the afternoon. The bike is going better than last year and we have a great setup.
"For tomorrow we still have a margin to improve the bike to suit my riding. I hope it won't be raining on Sunday, so let's hope the weather forecasts improve."