Nico Rosberg claimed another free practice session for the Williams team, but his run to the top of the Shanghai timesheets was not without incident.
Indeed, the German appeared the least likely candidate for P1 after putting his car into the gravel at the end of his sighting lap, falling victim to the same pit-lane entry that played a part in Lewis Hamilton's 2007 world title miss.
Unlike the Briton, however, Rosberg was eligible for outside assistance and, once his car had been lugged back to the garage, dusted down, checked over and fitted with a fresh set of Bridgestone, its pilot set about making up for his gaffe, edging closer and closer to the top of the times, before eventually usurping Jarno Trulli to make it six fastest times in nine sessions this season.
Rosberg left the target time at 1min 36.133secs as the field, generally, failed to go quicker than it had on Friday. Although some members managed to find time over their opening day efforts, the ultimate pace remained half a second shy of Jenson Button's best effort.
Trulli ended the hour-long outing 0.139secs back from Rosberg, but both Toyota and Brawn appeared to be working on things other than outright pace, confident perhaps of making the final phase of qualifying without having to take extreme measures. As a result, Button finished the session fourth overall, with countryman Hamilton returning to the top three as he continued with the revised McLaren, albeit now with a fresh engine.
Team-mate Heikki Kovalainen may have been running the same powerplant as on Friday, but finally achieved parity with the world champion in terms of updates, running the new front wing and interim diffuser to seventh spot.
That put the Finn behind the surprising Nelson Piquet Jr - who may well have taken the opposite tack to Brawn and dumped a load of fuel in search of possible Q3 necessary pace - and Felipe Massa, who gave Ferrari some encouragement, but may well have followed a similar route to his young countryman.
Piquet's team-mate, former double world champion Fernando Alonso, was another to try out revisions to his car, but the Renault R29 did not appear to gel as well with its latest diffuser as did the McLaren, leaving Alonso - who also decided to remove his KERS advantage - a disgruntled 19th fastest, ahead only of Timo Glock, who was sidelined early by a suspected gearbos problem, which could yet result in a five-place grid demotion.
Behind Kovalainen, Kimi Raikkonen and Rubens Barrichello rounded out a tight top ten - the Brawn man just half a second from Rosberg's benchmark - while Nick Heidfeld, a KERS-less Robert Kubica and Toro Rosso twins Sebastien Buemi and Sebastien Bourdais were only another tenth further back.
Behind the Red Bull 'junior' team, seniors Mark Webber and Sebastian Vettel both fell foul of identical driveshaft problems that forced the team to park the RB5s as a precaution lest the gremlins affect the gearbox under greater running.
Adrian Sutil and Giancarlo Fisichella slotted in ahead of Alonso and Glock in the final order.