PITTSBURGH (AP) -- Pittsburgh Pirates right fielder Gregory Polanco stepped into the batter's box with the bases loaded and one out in the fourth inning. His team led the Miami Marlins by a run, and he had a golden opportunity to put the game out of reach.
After taking two pitches out of the zone, he fouled one back behind the third-base dugout. The next was hit foul down the left field line.
Polanco's third cut did the trick as he laced left-hander Brian Flynn's 2-2 offering to his opposite field for a two-run single that gave the Pirates a three-run lead.
The rookie finished 2 for 4 and drove in four runs, Edinson Volquez pitched one-hit ball over seven innings, and Pittsburgh beat Miami 7-2 Thursday night.
''I was just trying to see the ball and not hurry with my swing,'' Polanco said. ''He was throwing really good. That's why I was fouling off so many balls.''
Polanco is showing he can handle left-handers early in his big league career.
''I think that's the third time he's shown that ability to hit a ball into left field off a left-hander,'' Pittsburgh manager Clint Hurdle said. ''When they're throwing down and away, he stayed out over the plate and covered it.''
Miami manager Mike Redmond said Jennings had his eyes open and was responding to questions when he was on the mound.
After the game, the Marlins announced that a CT scan on Jennings was negative and that he was diagnosed with a concussion. He was kept in a hospital overnight for observation.
Jennings momentarily stumbled before going to his knees after the play. He stood up to get in a cart and held up a hand to acknowledge the crowd as he was driven off the field.
Volquez (9-7) didn't allow a hit until the fifth, when Donovan Solano singled with one out. Volquez struck out seven batters and walked three.
Flynn (0-1) was chased before he got an out in the fifth.
Mercer's leadoff double started a three-run fourth. Polanco's two-run single made it 3-0.
Mercer and Gaby Sanchez added RBI singles in the fifth. Mercer finished with three hits and scored twice, and Josh Harrison extended his hitting streak to a career-high 11 games.
Polanco hit a two-run double in the eighth.
Giancarlo Stanton hit his 27th homer of the season, a two-run drive in the ninth for the Marlins.
''It's just one of those nights,'' Redmond said. ''We've got to be able to swing with these guys and we weren't able to do it.''
Marlins: 1B John Baker was held out of the game after fouling a ball off his foot Wednesday night.
Pirates: Center fielder Andrew McCutchen (rib) missed his third straight game. Hurdle said the reigning MVP is adding to his recovery routine but it is still in a ''wait-and-see'' situation as to whether he will go on the disabled list. ... Second baseman Neil Walker (back) sat out for the fourth time in five games. ... Infielder Clint Barmes (groin) is nearing a return, with baserunning being the only obstacle in the way of a plan to come off the DL.
Marlins: RHP Nathan Eovaldi (5-6, 4.22 ERA) starts for the Marlins against RHP Mike Leake (9-9, 3,46 ERA) on Friday night as Miami continues its six-game trip in Cincinnati. Eovaldi makes his second career start against the Reds. He pitched seven innings and allowed a run on two hits in Miami's extra-inning win Saturday.
Pirates: Pittsburgh opens a three-game set with San Diego at home as RHP Vance Worley (4-1, 2.43 ERA) faces RHP Ian Kennedy (8-9, 3.59 ERA). Worley has allowed just one run in his last two starts, which included his first career shutout on July 28 in San Francisco.
GETAWAY DAY STRIKE ZONE
Of Volquez's seven strikeouts Thursday night, four were called third strikes. After Volquez one-hit the Miami Marlins for seven innings, Redmond thought the Pirates' right-hander received aid from the umpire,
''He got some help back (behind the plate) too,'' Redmond said. ''He got some strike calls there. A lot of them.''