Valentino Rossi put his impressive late showing in second MotoGP practice at Motegi down to set-up changes on his Ducati.
The Italian had been challenging for the fringes of the top 10 when, with four minutes to run, he suddenly jumped into third, which at the time put him less than four tenths of a second off the ultimate pace.
The Italian, who first won at the Japanese circuit back in 2011, said his improvement came as a direct result of improving wheelspin under acceleration, a long-standing issue for Ducati.
"Today went pretty well, especially in the afternoon because we made a set-up change that helped us to improve grip on acceleration," the Italian explained.
"When I open the gas I'm able to exit the turns better, without spinning too much, and that's why I went pretty fast.
"I'm especially happy because the gap isn't too big."
Rossi cautioned however that Ducati still had to work on its long-run pace, focussing in particular on tyre degradation.
"Tomorrow, though, we'll have to improve our pace as well, because for now I'm able to ride well for some laps, and then the tyre starts to slide a bit too much," he said.
"The rear-tyre choice will be very important because the performance of the soft and the hard are very similar.
"The soft works a little better but we have to understand if it can last the race distance.
"Tomorrow we'll try some more changes and then we'll also consider the temperature for Sunday when making a decision."
Team-mate Nicky Hayden meanwhile said a combination of his hand injury and setup concerns had prevented him from matching Rossi's progress.
"It was a difficult day," he admitted. "This morning we weren't so far off, but I didn't improve in the afternoon.
"I'm not getting the feedback from the bike that I'd like under braking. Also, my hand is giving me some pain and I don't have a lot of strength, especially into the right-handers.
"There's lots of hard braking on this track, so I'm losing time mainly on the corner entry, and it's hard to recover on the exits. We need to have a re-think tonight and try to do a good step tomorrow."
- Valentino Rossi