Jakub Smrz denied Jonathan Rea a clean sweep of the Wednesday Portimao World Superbike test timesheets on his very last lap of the afternoon session.
Rea, riding in his new Castrol Honda colours, had dominated the two track sessions and looked set for a perfect start to 2011 after successfully repelling the afternoon challenge of Carlos Checa, Tom Sykes and rookie Eugene Laverty.
However Smrz - second fastest to Rea in the morning - put the new Liberty Ducati team ahead as he leapt from seventh to first place by 0.173sec. Prior to that 25th and final lap, Smrz had failed to improve on his morning time.
Smrz, just 13th in last year's world championship, set a best lap of 1min 43.503sec, which compares with the official Portimao WSBK race lap record of 1min 42.772sec, set by Max Biaggi in last year's event.
Behind the top two, new factory Yamaha rider Laverty made extraordinary progress as he improved from 14th in the morning to third place and just 0.204sec from Smrz in the afternoon.
While Smrz improved by 0.61sec, Laverty slashed over two-seconds from his morning lap time.
Tom Sykes showed Kawasaki had been wise to retain his services for 2011 with a confident fourth on the new ZX-10R, making it four different manufacturers in a top four covered by just 0.267sec.
First of the 'repeat' bikes was the Althea Ducati of Checa, who almost matched Laverty progress as he rose from just 15th in the morning - after a fall from his 1198 - to fifth in the afternoon.
Checa was the only rider other than Rea and Smrz to lead the afternoon session, when he briefly replaced Rea with just over an hour to go but lost ground in the closing stages.
Reigning world champion Biaggi began the test with third in the morning on his factory Aprilia, then didn't improve for much of the afternoon, until a late burst promoted the Italian star to sixth.