But Thursday night, with the Nats on the brink of playoff elimination and a lineup yet again showing little indication of emerging from a series-long slump, Zimmermann supplied something completely new: a jolt of unbridled, game-altering energy in a 2-1 Game 4 National League Divisional Series win over the Cardinals.
Ross Detwiler had supplied the first sufficient effort from any Nationals starter this postseason, tossing six innings of three-hit ball and allowing only one unearned run. Typically, a start like that is a fine recipe for a postseason victory. But with the Cards' Kyle Lohse equally dominant and the Nats' bats managing only two hits through eight innings, something else was needed to push Washington off the brink of elimination.
The third-largest crowd in Nationals Park history -- 44,392 fans once again armed with red "Natitude" rally towels for the second postseason game in Washington since 1933 -- had been lulled into suppression by the absence of offensive firepower.
Detwiler had thrown a career-high 104 pitches by the end of the sixth inning, forcing manager Davey Johnson to make a move. Thanks to poor efforts from his starting pitchers -- Zimmermann included -- in Games 1-3, Johnson had already taxed his bullpen against St. Louis' deep and seasoned lineup. So Zimmermann, the Nats' No. 3 starter all year behind Strasburg and Gio Gonzalez, knew he'd be available from the bullpen, though that was about it.
"I didn't really know what was going to happen, when they were going to use me or what the plan was," Zimmermann said. "But I was ready, and the call came."
Zimmermann trotted out from the right-field bullpen to a rousing ovation. His first pitch to Pete Kozma was a 96-mph fastball the Cardinals shortstop could only foul away. Three pitches later, Kozma whiffed on a 97-mph four-seamer from Zimmermann, perhaps the hardest he's thrown this season.
"It was special to watch," Tyler Clippard said. "I haven't seen him hit 97 all year."
It didn't stop there. Zimmermann hit 97 on four more pitches -- on the first to Lohse, who eventually struck out on four pitches, and then on the final three to Jon Jay, who could only look as another heater flew by.
Having aced his first and likely only relief appearance for a while -- Zimmermann said he had pitched in relief only once in the Minor Leagues -- he stepped off the mound with clear exuberance.
"Adrenaline just took over," Zimmermann said. "I was just trying to locate and trying to calm the emotions as much as I could, just trying to locate the fastball."
"He came in, and I mean, he was hyped," Johnson added. "That's the hardest I've seen him throw all year. I mean, his slider was like 91. Some guys in our club said, 'That's our next closer.' I said, 'No way.'"
Truth be told, the typically serene Zimmermann appears to have anything but a closer's mentality. In front of his locker after the game, the Auburndale, Wis., native wore a persistent grin across his face, but wasn't shy about calling the experience "nerve-wracking."
"I talked to [reliever] Craig [Stammen], I said, 'I don't know if I can do this for the rest of my life, so I better just stick to starting,'" Zimmermann said. "He was just like, 'Yeah, you know, you've got to start getting loose in the fourth, fifth [innings], stretch out a little bit.' He kind of walked me through it."
Clippard, a first-time All Star following a brilliant first half to the season as the Nats' closer, entered in the eighth. After Zimmermann had struck out the side, Clippard added two more before allowing a walk to Allen Craig. But Clippard regrouped to strike out Yadier Molina on three pitches, once again spurring the Nationals Park crowd onto its feet with several emotion-laden fist pumps of his own.
"The game was so tight all game long," Clippard said. "To get those strikeouts in those moments, I think, kept the momentum on our side, even though it was still tied."
At that point, the game had adopted the feel of one those where the next team to score would walk away victorious.
The Nats put only one runner on base in the bottom of the eighth before Drew Storen took the mound for the ninth. He struck out David Freese and Daniel Descalso despite reaching full counts in both at-bats, ratcheting the stadium buzz even higher. Kozma came up next and worked another full count before working his third walk of the game, but Storen was able to elicit an inning-ending pop out from pinch-hitter Matt Carpenter.
In their three innings on the mound, the Nationals' relievers collected eight strikeouts, all in a span of nine at-bats. Jayson Werth's walk-off home run capped off a riveting 13-pitch at-bat, flooded the diamond with an elated Washington team and captivated an ecstatic capacity crowd, but none of it would've been possible without the resounding effort from Zimmermann, Clippard and Storen.
"All of them were throwing harder than I've seen them throw, although Clippard has had some rest, and Storen pitched the night before," Johnson said.
"They say I'm supposed to give a big speech before the game to get them all pumped up. No. These guys are pumped up. They don't need no motivation."
Mike Fiammetta is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.