Sebastian Vettel returned to the Red Bull and managed just an installation lap all day as the champions' problems returned with a vengeance on Day 3.
It looked as if the Red Bull Renault was turning a corner in the final pre-season test, but the failings for the German represented a huge setback.
According to BBC reporter Tom Clarkson, there were two separate issues affecting Vettel's day:
A battery problem stopped Vettel this morning and as the team fired up the RB10 to send him out again at 3pm local time, they discovered another problem. They wouldn't confirm what this secondary problem was, only that it will prevent any further running today. That points to an issue either within the power unit or the gearbox.
Meanwhile further up the grid Felipe Massa topped the timesheets in the Williams, underlining another encouraging set of numbers for the team.
His 1:33.258 was the quickest lap seen in seven days of testing in Bahrain so far.
Mercedes had to change an engine but Nico Rosberg was still busy out on track, posting the second-quickest time of the day, well ahead of Kimi Raikkonen and the rest, a couple of seconds adrift.
With plenty of incident and issues for drivers to resolve, the debate on how ready the teams will be for the first race of the season in two weeks time continued.
Maritn Brundle, Sky Sports F1 commentator and former driver, asked:
There is just one more day for the drivers and teams to fine-tune on the track.
Here are the day's times, as recorded by Autosport:
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