Felipe Massa set the fastest time of Formula 1 pre-season testing in Bahrain so far on Saturday, as Sebastian Vettel failed to complete a lap for Red Bull.
Williams focused on performance work for Massa's final day in the car before the Australian Grand Prix weekend, and late in the afternoon the Brazilian, on supersoft tyres, set the quickest time over the two tests at Sakhir this pre-season.
Nico Rosberg - who completed 103 laps despite losing most of the morning due to an engine change - also went out on supersofts and briefly stole top spot from Massa with around 15 minutes to go, but the Williams went back out and beat his time by 0.2 seconds.
At the other end of the timing screens sat world champion Vettel, who took over from Daniel Ricciardo following Red Bull's best day of pre-season so far.
However, there was no continuation of that momentum for Vettel, who stopped halfway round his out-lap after waiting nearly three hours to head out of the garage for the first time.
The RB10 was sent out again before lunch, but this time it only made it to the end of the pitlane before Vettel stopped and had to push the car back.
After that the Red Bull mechanics closed the garage doors, and the car did not reappear.
Sauber and Lotus were the other teams in trouble. The Swiss team managed one lap before Adrian Sutil pulled to a stop at the pit entry with smoke coming out of the C33, requiring an engine change that could not be completed in time for him to run again.
Romain Grosjean was back in the Lotus for the first time at this final test, and after electrical problems prevented him from running in the morning, his day ended after just 33 laps with an MGU-K problem that was too big to fix before the end of the running.
Bahrain F1 test in pictures
In terms of race simulations, Force India followed its programme from the past two days with Sergio Perez, giving Nico Hulkenberg set-up work to do in the morning before a race run in the afternoon.
Ferrari had a quiet morning on Kimi Raikkonen's final day in the car, and it finally managed to carry out some race simulation work with the Finn in the final two hours of the day.
That left just enough time for some short runs just before the end, which enabled the 2007 world champion to set the third-fastest time.
AUTOSPORT Live coverage of Bahrain testing resumes for the final day from 6am UK time on Sunday morning
Pos Driver Team/Car Time Gap Laps
1. Felipe Massa Williams-Mercedes 1m33.258s 99
2. Nico Rosberg Mercedes 1m33.484s +0.226s 103
3. Kimi Raikkonen Ferrari 1m35.426s +2.168s 87
4. Kevin Magnussen McLaren-Mercedes 1m35.894s +2.636s 88
5. Daniil Kvyat Toro Rosso-Renault 1m36.113s +2.855s 81
6. Nico Hulkenberg Force India-Mercedes 1m36.205s +2.947s 115
7. Jules Bianchi Marussia-Ferrari 1m37.087s +3.829s 78
8. Marcus Ericsson Caterham-Renault 1m38.083s +4.825s 117
9. Romain Grosjean Lotus-Renault 1m42.166s +8.908s 33
10. Adrian Sutil Sauber-Ferrari 1
11. Sebastian Vettel Red Bull-Renault 0