Pirates 9, Diamondbacks 4: Jordy Mercer doubled in the go-ahead run as Pittsburgh exploded for eight runs in the final two innings to stun host Arizona.

The Pirates tied it with a three-run rally in the eighth and grabbed the lead when Josh Harrison ripped a one-out double in the ninth and scored on Mercer’s double to left off Bo Schultz (0-1). Pinch hitter Michael Martinez singled to center to plate Mercer, who finished with an RBI and three runs scored, before Russell Martin added an RBI single and Travis Snider drove in a pair to cap the ninth-inning uprising.

Tony Watson (8-1) worked a perfect inning of relief to pick up the win while Harrison and Andrew McCutchen each recorded two hits and two runs scored as Pittsburgh jumped into second place in the National League Central, 2 1/2 games behind Milwaukee. Ender Inciarte hit his second home run for the Diamondbacks.

Arizona snapped a scoreless draw with a rally in the fifth when Inciarte sent a three-run blast into the pool area in right-center before David Peralta walked, stole second, moved up on the overthrow and scored on a wild pitch. The Pirates got on the board in the next half-inning when Mercer doubled and scored on Gaby Sanchez’s single to left.

Vidal Nuno allowed one run and three hits in six innings and left in line for his first win since joining Arizona early last month before the bullpen let it slip away. Harrison tripled with one out off Randall Delgado in the eighth and Mercer walked before McCutchen and Pedro Alvarez ripped back-to-back doubles to plate three runs.

GAME NOTEBOOK: Edinson Volquez started for Pittsburgh and was reached for four runs - three earned - and seven hits in 5 2/3 innings. … The Pirates improved to 4-4 on their 10-game road trip and evened the series at a game apiece. … Arizona relievers Delgado, Eury De La Rosa and Schultz combined to allow eight runs on 10 hits and three walks in three innings.