Tanner Bibee struck out a career-high 12 in six innings, Josh Naylor homered twice and had four RBI, and the Cleveland Guardians beat the Seattle Mariners 8-0 in a battle of American League division leaders on Wednesday night.

Bibee (5-2) struck out multiple batters in each of the first five innings, allowing three hits and one walk in 93 pitches. The right-hander had 11 strikeouts in his previous start on June 12 at Cincinnati, his first double-digit game in the majors.

“The breaking balls, cutter, slider, slur, all were working really good and I definitely got into a rhythm tonight,” said Bibee, who induced 20 swing-and-misses. “When certain pitches are working how I want them, it’s nice.”

Steven Kwan hit a two-run homer and José Ramírez and Bo Naylor each had two hits for the Guardians, who have won 22 of 31 games at Progressive Field this season.