Although Mark Webber continued to lead the way at Sepang on Friday afternoon, his advantage was massively reduced by McLaren's Jenson Button.
Webber dominated Friday's opening practice session for the Malaysian GP, comfortably 1.665s ahead of Lewis Hamilton.
And although the Red Bull driver was again quickest in the afternoon, it was only by 0.005s and, this time, it was McLaren's other driver who mounted the challenge.
Button clocked a 1:36.881 to take second place ahead of his team-mate Hamilton while Sebastian Vettel finished in fourth place.
Michael Schumacher was fifth for Mercedes GP, beating Felipe Massa and Nico Rosberg while Renault were quick to resolve their brake issues allowing Nick Heidfeld to take part in the session. He finished P8.
Report: Friday's second practice began on a hot track with the asphalt almost 50'C and one team short after Renault revealed they would not run until they know what caused their double brake failure in the morning's session.
The drivers were quickly out on track with Michael Schumacher taking the early advantage with a 1:40.657 before losing out to Feipe Massa then Rubens Barrichello and Lewis Hamilton. Pastor Maldonado was the next to lead the way, 0.019s up on Hamilton, as he did one flying lap on the soft tyres.
After the first half an hour, Maldonado was in the P1 slot ahead of Hamiton, Barrichello, Jenson Button, Schumacher, Nico Rosberg and Sergio Perez. The two Red Bulls were 15th and 16th with Sebastian Vettel ahead of Mark Webber.
Schumacher returned to the front with a 1:38.088 while Jaime Alguersuari claimed to second place, 0.758s behind the Mercedes GP driver. However, the Red Bull drivers then came to the fore with Webber taking the P1 slot with a 1:36.876 while Vettel improved to second.
Another failure for Hispania as Tonio Liuzzi parked his car on the side of the track. The Italian mounted the kerbs and appeared to have killed the electronics in his car. Not a great Friday for the backmarker outfit.
Maldonado's day came to an abrupt end when he lost control of his Williams, spun it and put it nose first into the Alliance (Williams' sponsor) barrier. Well, at least that's great advertising for Alliance.
With thirty minutes left in the session Webber was leading the way ahead of Button, Vettel, Schumacher, Massa, Rosberg, Fernando Alonso and Alguersuari. Schumacher kicked up the gravel at Turn Six after running wide but managed to avoid the barriers.
The drivers put in lap after lap as they got they feel for their Pirelli tyres and worked on set-up ahead of Saturday's qualifying and Sunday's race. Button closed the gap to Webber to just 0.005s while Hamilton took third place behind his team-mate.
The session ended with Webber at the top of the timesheets with his 1:36.879 and Button second ahead of Hamilton.
Times
01. Mark Webber Red Bull 1:36.876 24 laps
02. Jenson Button McLaren 1:36.881 30 laps
03. Lewis Hamilton McLaren 1:37.010 23 laps
04. Sebastian Vettel Red Bull 1:37.090 30 laps
05. Michael Schumacher Mercedes GP 1:38.088 26 laps
06. Felipe Massa Ferrari 1:38.089 31 laps
07. Nico Rosberg Mercedes GP 1:38.565 25 laps
08. Nick Heidfeld Renault 1:38.570 16 laps
09. Fernando Alonso Ferrari 1:38.583 27 laps
10. Jaime Alguersuari Toro Rosso 1:38.846 31 laps
11. Pastor Maldonado Williams 1:38.968 25 laps
12. Rubens Barrichello Williams 1:39.187 30 laps
13. Vitaly Petrov Renault 1:39.267 17 laps
14. Kamui Kobayashi Sauber 1:39.398 29 laps
15. Sergio Perez Sauber 1:39.603 34 laps
16. Paul di Resta Force India 1:39.625 31 laps
17. Adrian Sutil Force India 1:39.809 28 laps
18. Sebastien Buemi Toro Rosso 1:40.115 31 laps
19. Timo Glock Virgin Racing 1:40.866 24 laps
20. Jarno Trulli Team Lotus 1:41.890 19 laps
21. Narain Karthikeyan Hispania 1:43.197 15 laps
22. Vitantonio Liuzzi Hispania 1:43.991 14 laps
23. Heikki Kovalainen Team Lotus 1:44.886 4 laps
24. Jerome d' Ambrosio Virgin Racing no time
