DENVER
Jairo Diaz’s late-season audition for the role of setup man hit a bump Thursday.
Diaz gave up a go-ahead, three-run home run to Pedro Alvarez in the eighth inning, and the Pittsburgh Pirates rallied to beat the Colorado Rockies 5-4, completing a four-game sweep.
“It was a fastball away, but I missed,” Diaz said. “It was supposed to be away, but it was in the middle.”
Trailing 4-2 heading into the eighth, Starling Marte, who had four hits in the game, and Neil Walker each had one-out singles off Diaz (0-1). After a strikeout, the stage was set for the left-handed hitting Alvarez.
The Rockies had left-handed reliever Boone Logan up in the bullpen, but manager Walt Weiss opted to stick with the right-handed Diaz, a rookie who has been used extensively in a setup role since his Aug. 23 recall from Triple-A Albuquerque.
“Jairo’s been our guy in the eighth inning. He’s been lights out,” Weiss said. “He’s been better against lefties than righties, and Logan’s not going to face Alvarez there. They’re going to pull him back (for a right-handed batter). If I pull the string right there with Logan, go get him, it gives them the upper hand in matchups.”
Alvarez blew up the strategic approach by turning on Diaz’s mid-plate offering for his 26th home run of the season.
“There are a lot of what-ifs over the course of nine innings,” Weiss said. “Alvarez got a big hit for them. That’s what it came down to.”
Reliever Joe Blanton (5-0) earned the win for a second consecutive game. Mark Melancon pitched a perfect ninth to pick up save No. 50. He became the seventh National League closer to reach that total in a season.
Nolan Arenado had a two-run double in his return to the lineup. He sat out Wednesday after banging his head on the dirt when he dove for a ground ball Tuesday.
The Pirates entered the day four games behind first-place St. Louis in the NL Central. They rested third baseman Aramis Ramirez (groin) and Gregory Polanco (knee) with a big series in Chicago against the Cubs starting Friday.
Cristhian Adames broke a tie in the fifth with an RBI-triple into the left-center gap that scored Corey Dickerson.
Chad Bettis was in line for the win after allowing two runs over six innings, but the bullpen couldn’t hold it.
Jeff Locke threw 5 2/3 innings and gave up four runs in his 30th start this season, which matches his career high.
Rockies rumpus
OF Brandon Barnes could be done for the season after straining his left hamstring Wednesday. ... OF Charlie Blackmon missed a second consecutive game with neck stiffness. ... RHP David Hale (4-5, 6.32) will take the mound Friday, as Colorado will begin a three-game series against the Dodgers, who lead the NL West and can lock up the division title this weekend.
