Jenson Button was the driver to beat in Friday's first practice at Suzuka, which ended with Sebastian Vettel nose first in the barriers.
The McLaren driver, the last man standing between Vettel and his second World title, clocked a 1:33.634, which put him 0.091s up on his team-mate Lewis Hamilton.
Vettel finished in third place, 0.456s adrift of Button, in a session that never once again the Champion-elect hold the P1 position.
However, it did see him in the barriers as the German crashed in the final seconds of practice at the Degner curve. Running onto the gravel, Vettel's RB7 got away from him resulting in a minor coming together with the barriers.
Fernando Alonso was fourth for Ferrari, edging Mark Webber and Jaime Alguersuari while Felipe Massa and Sebastien Buemi completed the top eight.
Report: With the track temperature sitting at 30'C, Timo Glock led out the field for their standard installation laps with Narain Karthikeyan in action for HRT and Karun Chandhok behind the wheel for Team Lotus. Nico Hulkenberg was another test driver on track, driving Adrian Sutil's Force India.
Daniel Ricciardo posted the first time of the morning, a 1:46.073, to get proceedings underway. But, despite lowering his time, he was soon dropped by Kamui Kobayashi as the Sauber driver hit the front with a 1:38.123. With more drivers venturing out to get started on the hard yards, Mark Webber was the next in the P1 slot with Felipe Massa half a second behind.
Lewis Hamilton soon overhauled Webber with a 1:36.110 only to lose out to Fernando Alonso moments later. Webber upped his pace to take second. Michael Schumacher claimed seventh on his first lap, Sebastian Vettel went P8 and then Jenson Button went fifth.
Button was the next to lead the way, lowering the benchmark time to a 1:33.648 as he went ahead of Hamilton, Aloso, Webber, Vettel and Jaime Alguersuari. Massa, Schumacher and Sebastien Buemi completed the top eight at the halfway stage.
Vitaly Petrov was the last man to post a time, a 1:38.082, which put him P14. The Renault driver continued lapping, improving his time to take 11th and then 10th place.
With the wind picking up quite noticeably, Vettel improved to fourth place, leapfrogging his Red Bull team-mate. As long as the German finishes in the points this weekend, even just one point, he will win the World title.
Not many improved their times in the latter stages of Practice One, although Button did manage to lower the benchmark by a couple of tenths.
And Vettel ended the session nose-first in the barriers after spinning on the gravel at the Degner curve. The damage to his car was not significant.
Times
01. Jenson Button McLaren-Mercedes 1m33.634s 20 laps
02. Lewis Hamilton McLaren-Mercedes 1m33.725s + 0.091 18 laps
03. Sebastian Vettel Red Bull-Renault 1m34.090s + 0.456 22 laps
04. Fernando Alonso Ferrari 1m34.372s + 0.738 24 laps
05. Mark Webber Red Bull-Renault 1m34.426s + 0.792 25 laps
06. Jaime Alguersuari Toro Rosso-Ferrari 1m34.937s + 1.303 23 laps
07. Felipe Massa Ferrari 1m35.585s + 1.951 27 laps
08. Sebastien Buemi Toro Rosso-Ferrari 1m35.590s + 1.956 25 laps
09. Michael Schumacher Mercedes 1m36.033s + 2.399 22 laps
10. Vitaly Petrov Renault 1m36.370s + 2.736 18 laps
11. Bruno Senna Renault 1m36.487s + 2.853 18 laps
12. Nico Hulkenberg Force India-Mercedes 1m36.700s + 3.066 21 laps
13. Kamui Kobayashi Sauber-Ferrari 1m36.948s + 3.314 24 laps
14. Paul di Resta Force India-Mercedes 1m36.949s + 3.315 22 laps
15. Sergio Perez Sauber-Ferrari 1m37.103s + 3.469 29 laps
16. Nico Rosberg Mercedes 1m38.197s + 4.563 18 laps
17. Rubens Barrichello Williams-Cosworth 1m38.331s + 4.697 11 laps
18. Pastor Maldonado Williams-Cosworth 1m38.446s + 4.812 8 laps
19. Jarno Trulli Lotus-Renault 1m39.168s + 5.534 10 laps
20. Karun Chandhok Lotus-Renault 1m39.946s + 6.312 22 laps
21. Timo Glock Virgin-Cosworth 1m40.872s + 7.238 13 laps
22. Jerome D'Ambrosio Virgin-Cosworth 1m41.019s + 7.385 24 laps
23. Daniel Ricciardo HRT-Cosworth 1m41.106s + 7.472 25 laps
24. Narian Karthikeyan HRT-Cosworth 1m41.775s + 8.141 25 laps
