"Including the at-bat before, he threw me four straight sliders," Piscotty said afterward. "I'm just trying to get a good pitch over the middle of the plate, and I put a good swing on it."
The Cardinals' five-run rally began with one out, when pitcher Jaime Garcia singled to right field. Greg Garcia walked, Aledmys Diaz singled and Matt Holliday walked, forcing home one run and bringing Piscotty to the plate. Piscotty launched the second pitch of the at-bat into the left-field seats.
Scherzer had previously gotten Piscotty to pop up a slider in the first inning and induced a foul tip on a slider to start their third-inning matchup, but when he went to the pitch again, Piscotty punished him.
"It was a dumb pitch," Scherzer said. "I hadn't shown my fastball yet and I threw another slider and I hung it. He put a good swing on it, ended in a blast."
The grand slam ended up being enough offense for the Cardinals, who added an insurance run in the eighth but held the Nationals to two scores.
After impressing the Cardinals during a second-half callup last season, Piscotty has been one of St. Louis' best hitters in 2016. The outfielder's .324 batting average ranks second to Aledmys Diaz (.327) on the team among regulars, and his .901 OPS places him third. He has been a focal point of a Cardinals offense that leads the National League in runs.
"That's the offense that I believed we would have in the winter, and everyone kind of snickered, I believe," Cardinals manager Mike Matheny said. "There hadn't been a lot of production in the past to prove this is a team that has power, has the ability to throw up big runs. You just could see the pieces were there for this to come together."
Alex Putterman is a reporter for MLB.com based in Washington.