Pirates 7, Rockies 5: Josh Harrison and Gregory Polanco hit back-to-back home runs to open the eighth inning as Pittsburgh avoided a three-game sweep in Colorado.

After Nolan Arenado tied the game at 5-5 with a solo shot in the seventh, Rex Brothers (3-5) gave the lead right back to the Pirates on the first pitch of his outing in the eighth when Harrison lifted a fastball over the fence in right-center. Polanco padded the lead moments later, crushing a 2-1 slider into the seats in right.

Tony Watson (7-1) gave up Arenado’s blast among his three hits over the seventh and eighth innings and Mark Melancon brought an end to the three-hour, 58-minute affair in the ninth with his 19th save for Pittsburgh, which got two RBIs apiece from Harrison (four hits) and Polanco to end a five-game losing streak in Colorado in which it was outscored 35-9. Brandon Barnes homered and DJ LeMahieu tallied three hits for the Rockies.

After Pirates starter Edinson Volquez drew a walk in the second to load the bases with one out, Harrison grounded past short to plate Jordy Mercer and Polanco followed with a sacrifice fly. LeMahieu halved the lead with a two-out RBI single in the bottom half before Colorado used a two-run blast by Barnes and a run-scoring double from Charlie Blackmon to pull ahead 4-2 in the fourth.

Colorado starter Franklin Morales was pulled after issuing a pair of walks to open the fifth, but Arenado helped reliever Chad Bettis get out of a bases-loaded jam with no outs when he snagged Mercer’s liner and slid into third to beat Andrew McCutchen for an unassisted double play. Bettis was less fortunate in the sixth, surrendering a pinch-hit two-run homer to Travis Snider and Ike Davis’ go-ahead, two-out RBI double.

GAME NOTEBOOK: Harrison was awarded two stolen bases on the same play in the sixth when he slid past second, but was not tagged out by Rockies SS Josh Rutledge. After forcing five throws in a rundown, Harrison reached third safely when C Wilin Rosario fell down as he went to tag him. … The Colorado bullpen has given up at least one earned run in a season-high 12 consecutive contests. … Rockies RF Carlos Gonzalez went 0-for-2 after coming in as a defensive replacement in the sixth inning. He rolled his ankle and was a late scratch prior to Saturday’s victory.