Daric Barton’s two-homer, six-RBI night supported Trevor Cahill’s 18th victory as the Oakland Athletics pounded the Seattle Mariners 9-0 Friday night at Safeco Field.

Barton set career highs in homers and RBI in his first two at-bats. The left-handed hitter belted a solo homer in the first inning off Seattle starter Luke French and added his 10th bomb of the season and first career grand slam in the second as Oakland pulled out to a 7-0 lead.

For good measure, the American League’s leader in walks (110) drove in another run with a double in the sixth.

Cahill (18-8) allowed just five singles and two walks with six strikeouts in seven frames to end the season on a good note after late-season struggles knocked him out of Cy Young contention.

Cahill is the first pitcher 22 years of age or younger to reach 18 wins since Mark Prior of the Chicago Cubs in 2003, and he is the youngest 18-game winner in team history since Vida Blue recorded 24 wins in 1971.

Oakland has swept the first two games of this series and needs to take the final two to finish .500 for the first time since 2006.

French (4-4) was torched for eight runs and eight hits in four innings to drop to 0-3 against Oakland this season.