Chaz Davies bounced back from injury to take his fourth win of the 2017 World Superbike season, after the Ducati rider held championship leader Jonathan Rea at bay for race once success at Laguna Seca.
Davies has been on the pace all weekend despite still suffering pain from a back fracture he sustained in a horror collision with Rea at Misano.
Off the line, the Welshman nipped ahead of the Kawasaki rider, and fended off an early attack into Turn 5 to hold onto second, while pole man Tom Sykes darted six tenths into the distance at the head of the pack.
Rea briefly took second away from Davies at the final corner, but was re-passed into the Andretti hairpin on the second lap.
By now Sykes had built himself a gap of almost a second, but with Rea held at bay Davies rapidly closed the Yorkshireman down, and took the lead away from him with a daring pass into Corkscrew on lap 12.
The Ducati rider forced Sykes to pick the bike up mid-corner, curbing his momentum on the run down to Rainey corner and giving Kawasaki team-mate Rea a run on him, which he utilised to take second.
The top two immediately gapped Sykes, who fell 5.7 seconds back from the win at the chequered flag in third.
For the remainder of the second half of the race, Rea stalked Davies, attempting several passes, all to no avail.
A fastest lap from Rea of 1m23.533s with five to go kept Davies under pressure, but the Kawasaki rider could do nothing to halt the Welshman’s charge – Davies taking the chequered flag 1.2 seconds clear.
The win for Davies sees him claw five points back on Rea, though the Kawasaki rider’s gap still stands at a sizeable 106 points. Sykes slips 54 points adrift in second in the standings.
Marco Melandri fell off the lead group in the early stages of the 25-lap contest and crossed the line a distant fourth, the Italian securing pole for Sunday’s reversed grid race.
Xavi Fores completed the top five, the Barni Ducati rider fending off a late charge from Leon Camier on his MV Agusta.
Jordi Torres prevailed in a tight scrap for seventh ahead of Michael van der Mark, Leandro Mercado and Lorenzo Savadori, while Stefan Bradl fended off Roman Ramos, Raffale De Rosa, Alex De Angelis and debutant Jake Gagne for 11th.
Milwaukee Aprilia’s Eugene Laverty was set for a top five result in race one, but crashed on lap 11 at Turn 3. He joined fellow Brit Alex Lowes on the sidelines, the Yamaha rider’s day ending on lap seven at Turn 5.