He faced 28 Marlins and threw 23 of them a first-pitch strike. In doing so, he turned what was supposed to be a postseason tuneup into a pitching clinic.
And when he was finished, he had done something else: He reminded all of us that he's playing on a baseball team that's scary good -- tremendous rotation, deep offense, great leadership.
This whole team is a joy to watch. Also -- and this is critical -- the Nationals are playing their best at the most important time of the year.
They've slid under the radar a bit as attention focused on the teams scrambling to grab a postseason berth. The Nationals had long since taken care of their business, clinching the National League East in their 150th game and sewing up home-field advantage in the NL Championship Series on Friday.
You probably already know the larger story of the Nationals. They've been constructed methodically and smartly, with a great general manager, Mike Rizzo, and a plan that could serve as a blueprint for every other team.
Between 2008-10, the Nationals averaged 99 losses a season. This happened right after they hired Rizzo, who eventually would be put in charge of their entire baseball operation.
His plan was to pour resources into the Draft and the farm system, and he would accept some short-term pain to build a great franchise. He wanted to accumulate power arms, and if you've watched much of the Nationals the last three seasons, you already know this.
What you're seeing today is the end result of all that smart work. Over the last three seasons, the Nationals have won more games than any other team (280). They also have the best ERA in the Majors (3.31) over that time.
And they're celebrating a second division title in three seasons. Before Zimmermann stole the show, Sunday was supposed to be a day of celebration for the Nats.
Manager Matt Williams pulled his regulars one at a time, allowing curtain calls and a chance to turn the afternoon into a pre-playoff pep rally of sorts.
The Nationals will be the first to tell you that baseball is different in October. Their manager calls it "a completely different animal." He speaks from the experience of having played on and coached World Series teams.
Baseball's best teams grind through the regular season, immune to the highs and lows of small storms. They play on, thriving on the routine and the competition.
And then there's the postseason.
Suddenly, everything that happened in the first six months means nothing. Everything becomes magnified. There is no normal.
Baseball's top dozen teams are so close in terms of talent and confidence that October is a new beginning.
"There's almost no difference between the teams that are good enough to make the [final eight]," Nationals third baseman Ryan Zimmerman told the Washington Post's Thomas Boswell. "That's what makes baseball so much fun to watch in October. It's such a game of streaks. Who gets hot? Can any one team win three out of five from any other? Come on, of course."
The Nationals learned this tough lesson in 2012, when they had the best record in baseball (98-64) and were eliminated by the Cardinals in the NL Division Series.
This is not unusual. Since 2000, only two teams that had the NL's best record got to the World Series. Neither of them won it.
This competitive balance makes for great theater and plenty of heartburn. But the best way to evaluate a team is how it has played for an entire season and how it's playing now.
That's why the Nationals seem to be the team to beat, at least at the start. They've got the best record in baseball (71-39) since May 30 and the best in September (19-8). Their normal five-man rotation -- Zimmermann, Stephen Strasburg, Doug Fister, Gio Gonzalez and Tanner Roark -- is 13-0 with a 0.89 ERA in its last 13 starts.
Offensively, Denard Span, Anthony Rendon, Jayson Werth and Adam LaRoche are capable of taking over a postseason series.
This may be the postseason when the kid introduces himself as one of the next great players in baseball.
The Nationals climbed alone atop the NL East on July 21 and spent a total of 119 days there. They simply couldn't be any more prepared. This might just be their moment.
After Zimmermann's no-hitter, Span summed up the thoughts of an entire clubhouse.
"Epic day for an epic season," he said.