The Australian was joined on track by team mate David Coulthard, who finished in seventh. Although strong winds at the circuit prevented the team from carrying out any meaningful aerodynamic work on the RB4, the duo covered over 150 laps during the day. Both will be in action again on Thursday.
In the second Williams was Rosbergs team mate Kazuki Nakajima, who took the third-fastest slot. The British team continued to focus on the development of the FW30 and Rosberg and Nakajima covered 98 and 91 laps respectively.
Fourth fastest was Fernando Alonso for Renault. Despite suffering a few minor problems in the morning, Alonso completed over 100 laps as he tested parts for the R28. Team mate Nelson Piquet Jr was equally productive, covering 110 laps, and taking up ninth slot on the timesheets.
Robert Kubica was once again the quicker of the two BMW Sauber drivers, finishing fifth fastest, while team mate Nick Heidfeld ended in 11th. With no major problems to interrupt their running the duo covered 116 and 109 laps. The team, however, did opt to abandon plans for long runs in the afternoon due to the strengthening winds.
Fastest man from Tuesday, Lewis Hamilton, took up sixth slot, while McLaren team mate Heikki Kovalainen finished in tenth. Hamilton and Kovalainen were both tasked with carrying out longer runs in the MP4-23 and the duo covered 152 laps in total.
Eighth quickest was Sebastian Vettel for Toro Rosso, while Vettels team mate Sebastien Bourdais finished in 12th. During the day both STR2Bs ran with the latest front suspension spec and the team focused their attentions on aero testing and car balance. Vettel completed 114 laps, but Bourdais morning session was hampered by mechanical problems and the Frenchman was limited to 76 laps.
Honda continued to struggle to make much of an impression on the times, with Jenson Button finishing in 13th and Rubens Barrichello in 15th. Chassis work and set-up evaluations dominated the teams programme and Button and Barrichello covered over 130 laps.
Completing Wednesdays line-up was Takuma Sato in 14th for Super Aguri and Adrian Sutil in 16th for Force India. Sato used his last day in the SA07B at Jerez to run a series of set-up optimisation tests. He will hand over testing duties to Anthony Davidson on Thursday. For Force India, Sutil carried out race simulation work and evaluated the reliability of several new parts.
Testing continues at Jerez on Thursday.
Unofficial Wednesday times from Jerez:
1. Mark Webber, Red Bull, 1:18.628
2. Nico Rosberg, Williams, 1:19.091
3. Kazuki Nakajima, Williams, 1:19.215
4. Fernando Alonso, Renault, 1:19.710
5. Robert Kubica, BMW Sauber, 1:19.829
6. Lewis Hamilton, McLaren, 1:19.857
7. David Coulthard, Red Bull, 1:19.883
8. Sebastian Vettel, Toro Rosso, 1:19.889
9. Nelson Piquet Jr, Renault, 1:20.014
10. Heikki Kovalainen, McLaren, 1:20.152
11. Nick Heidfeld, BMW Sauber, 1:20.201
12. Sebastien Bourdais, Toro Rosso, 1:20.536
13. Jenson Button, Honda, 1:21.147
14. Takuma Sato, Super Aguri, 1:21.376
15. Rubens Barrichello, Honda, 1:21.710
16. Adrian Sutil, Force India, 1:22.244
