Jonathan Rea had to settle for second place once again as Alvaro Bautista claimed his seventh straight win in this season's World Superbike championship.
Bautista led from start to finish at Aragon with Rea finishing ahead of the Spaniard's Aruba Ducati teammate Chaz Davies.
Bautista and Rea have finished 1-2 in every single race this season.
The former MotoGP star extends his lead over Rea in to 31 points, with a 10-lap race and race two to come on Sunday.
"I managed to reach fifth by the end of turn two on the first lap and settled into a nice rhythm with Chaz and the Yamaha boys," Rea said afterwards.
"I made some ground on the early parts of the laps but in the last sectors the other bikes had the legs on us.
"I tried to be perfect on the last lap and go into the long straight with a bit of a gap and I managed that."was second in the opening World Superbike race of the weekend at Aragon as Alvaro Bautista made it seven wins from seven starts this season.
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Four-time world champion Rea started Saturday's race from 10th position on the grid.
Despite being nudged by German rider Markus Reiterberger at the start, Rea progressed through the field and finally got the better of Welshman Davies.
Bautista finished the race 15.17 seconds ahad of Rea to become the first Spanish rider to win in Spain since Ruben Xaus 12 years ago.
Meanwhile, Eugene Laverty had to settle for a point after making contact with another rider on the final lap and sliding into the gravel.
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