Team USA won the eighth inning versus Venezuela, but the nine-hole hitter's stroke proved crucial.
USA loaded the bases with nobody out against left-hander José Quijada, trailing Venezuela by two runs.
Tim Anderson walked, Pete Alonso singled, and J.T. Realmuto was hit.
Venezuela manager Omar Lopez replaced Quijada with right-hander Silvino Bracho, who faced a nightmare.
Bracho would try to strike out his first hitter, but Mookie Betts and Mike Trout were waiting behind him.
But, Trea Turner, a gifted nine-hole hitter, started the game. Turner was rapidly down 0-2 against Bracho, but he didn't care.
Turner hit a grand slam to left field on his third pitch to put the team ahead 9-7 in the eighth inning.
Turner later declared the grand slam was his greatest baseball accomplishment, which is impressive considering he had 44 hits in 27 playoff games.
Turner called it his loudest game. "Today was electrifying and comparable to World Series games."