Rookie left-hander Jeff Locke makes the third start of his game series at PNC Park.
A second-round pick of the Atlanta Braves in 2006, Locke was 8-10 in 28 appearances in the minors this season, posting a 3.70 earned run average and striking out 139 batters in 153 1/3 innings.
He made his initial big-league start at home against Florida on Sept. 10 and took a 3-0 loss, then returned six days later for a 7-2 loss to the Dodgers in Los Angeles.
In eight combined big-league innings, Locke has allowed 10 hits and six runs while walking six and striking out one.
The Reds start 28-year-old Edinson Volquez, who's lost three consecutive starts.
The former National League All-Star, who last won on June 29 at Tampa Bay, was sent to the minors after an 8-1 loss in St. Louis on July 5. He returned for a 4-1 loss at Colorado on Sept. 11 and was tagged for five runs and six hits in 6 2/3 innings of a 10-1 loss to Milwaukee on Sept. 17.
Volquez is 1-0 in six career starts against the Pirates with a 3.44 ERA.
Arroyo (9-12) gave up six hits and recorded his first shutout since August 2009. The right-hander struck out two and did not issue a walk in his first win this season since Aug. 24.
Pirates starter Ross Ohlendorf (1-3) was chased from the game in the third frame when he loaded the bases without recording an out. He went two-plus innings, allowing seven runs on seven hits and two walks.
Derrek Lee continued to swing a hot bat for Pittsburgh, going 3-for-4 with a home run and two RBI.
Pittsburgh is 8-4 versus the Reds this season.