Carpenter’s homer was the 15th by a St. Louis pinch-hitter this season, a major league record. Yadier Molina went 4 for 5, including a first-inning grand slam. Mike Mayers (1-1) tossed a scoreless eighth for the win, and Seung-Hwan Oh worked around a solo homer to Jung Ho Kang in the ninth for his 16th save.

The Pirates came in reeling during their longest skid in two years, one that dropped them to the fringe of playoff contention. Opponents outscored them 47-22 during the slide, including a 12-6 setback on Monday night in which the Cardinals simply overpowered Pittsburgh’s struggling pitching staff.

It looked like more of the same early on Tuesday. The Cardinals loaded the bases against Ryan Vogelsong thanks in part to a moment of hesitation by first baseman John Jaso in which Jaso tried to throw out Kolten Wong at third rather than tag first for an easy out. Molina turned Vogelsong’s next pitch into his first grand slam since 2012, the 25th straight game the Cardinals have homered, a club record.

Adams pounded Vogelsong’s offering 436 feet over the stands in right in the second to put St. Louis up 5-0, but Pittsburgh scrapped back.

Jaso atoned with an RBI single in the second and Kang homered in the fourth to make it 5-2. Bowman entered for rookie Luke Weaver, pulled after four innings and 83 pitches, and quickly frittered the lead away. His wild throw to second on an attempted double play gave Pittsburgh life. Gregory Polanco followed with an RBI single, Andrew McCutchen scored when Brandon Moss couldn’t handle Matt Joyce’s line drive and Mercer doubled to the left-field corner to give the Pirates just their second lead in a week.

It didn’t last.

Watson, moved to the closer role after Pittsburgh sent All-Star Mark Melancon to Washington at the trade deadline, quickly retired the first two batters in the ninth and had Carpenter down 0-2 when Carpenter changed things completely with one swing.