Arrieta strikes out 11, Rizzo drives in 4, Cubs beat Pirates

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CHICAGO — 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.

Chicago Cubs starting pitcher Jake Arrieta works in the third inning against the Pittsburgh Pirates on Saturday, May 14, 2016, at Wrigley Field in Chicago. The Cubs won, 8-2, as Arrieta struck out 11, improving to 7-0 on the season. (Anthony Souffle/Chicago Tribune/TNS via Getty Images)

Chicago Cubs starting pitcher Jake Arrieta works in the third inning against the Pittsburgh Pirates on Saturday, May 14, 2016, at Wrigley Field in Chicago. The Cubs won, 8-2, as Arrieta struck out 11, improving to 7-0 on the season. (Anthony Souffle/Chicago Tribune/TNS via Getty Images)

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.

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.