Troy Corser tightened his grip on the World Superbike Championship crown in Brno on Sunday - but Noriyuki Haga stole the show in the Czech Republic.
Alstare Suzuki rider Corser won race one with ease and looked to be on course to double up in the second.
But Yamaha rider Haga came from 17th to pip Corser and claim one of the most unlikely wins in the series' history.
But Corser now holds a 94 point lead over Winston Honda's Chris Vermeulen, who finished eighth and third.
Reigning champion James Toseland finished in second place, seven seconds behind Corser, in race one, while Toseland's Ducati team-mate - Regis Laconi - fought his way up from ninth on the grid to take third.
But Toseland could only manage an eighth place in race two and the Briton now trails Corser by a massive 147 points - results which he concedes ends his bid to retain his crown.
"It's a pity," said Toseland, "but with Corser's results (in Brno) it looks as if we're not going to be able to win the championship now."
Chris Walker's fortunes mirrored countryman and former team-mate Toseland's,
with a strong first race giving him fourth place before trailing home 10th for
PSG-1 Kawasaki in the second.
Carl Fogarty's Foggy Petronas team suffered a weekend to forget, with neither
Steve Martin nor Garry McCoy picking up a single point.
McCoy's day went wrong when he clashed with Jose Luis Cardosa on lap five of race one and was hit by Mauro Sanchini.
The Australian sustained a cut elbow, hurt his ankle and suffered concussion and was duly ruled out of race two.
The injuries are also expected to prevent him testing in Germany this week.
1. Troy Corser, Australia, Suzuki, 41 minutes, 42.829 seconds.
2. James Toseland, Britain, Ducati, 41:49.421.
3. Regis Laconi, France, Ducati, 41:50.306.
4. Chris Walker, Britain, Kawasaki, 41:51.889.
5. Pierfrancesco Chili, Italy, Honda, 41:52.012.
6. Lorenzo Lanzi, Italy, Ducati, 41:53.607.
7. Noriyuki Haga, Japan, Yamaha, 41:65.589.
8. Chris Vermeulen, Australia, Honda, 41:57.898.
9. Norick Abe, Japan, Yamaha, 41:59.149.
10. Andrew Pitt, Australia, Yamaha, 42:02.505.
1. Noriyuki Haga, Japan, Yamaha, 41:43.526.
2. Troy Corser, Australia, Suzuki, 41:46.758.
3. Chris Vermeulen, Australia, 41:54.537.
4. Norick Abe, Japan, Yamaha, 41:55.793.
5. Pierfranco Chili, Italy, Honda, 41:55.886.
6. Lorenzo Lanzi, Italy, Ducati, 41:57.036.
7. Regis Laconi, France, Ducati, 41:57.666.
8. James Toseland, Britain, Ducati, 41:59.964.
9. Karl Muggeridge, Australia, 42:00.345.
10. Chris Walker, Britain, Kawasaki, 42:03.262.
(After seven of 12 rounds)
1. Troy Corser, Australia, 299 points.
2. Chris Vermeulen, Australia, 205.
3. Regis Lanconi, France, 187.
4. Yukio Kagayama, Japan, 158.
5. James Toseland, Britain, 152.