CHICAGO (AP) Unbeaten Jake Arrieta struck out 11 in eight innings, Anthony Rizzo drove in four runs and the Chicago Cubs remained perfect against the Pittsburgh Pirates with an 8-2 victory on Saturday.

Arrieta (7-0) improved to 18-0 in 20 outings since Aug. 1. The Cubs have won his last 21 starts, extending a franchise record.

Rizzo belted a towering three-run homer in the fourth and singled in Jason Heyward in the eighth. Heyward finished with three hits, Ben Zobrist reached four times and Addison Russell hit a two-run homer as major league-leading Chicago improved to 5-0 against Pittsburgh this year.

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Bouncing back from a so-so start for his lofty standards, Arrieta allowed two runs and three hits while moving to 8-1 in 11 career regular-season starts against the Pirates. The reigning NL Cy Young Award winner also struck out 11 in a five-hit shutout at Pittsburgh in last year's wild-card game.