Making his ninth career start, Wacha came oh-so-close to finishing off the third no-hitter in the majors this season. Instead, the Busch Stadium crowd let out a loud, collective groan as the rookie became the third pitcher to have an attempt broken up with one out to go.
"I guess it just wasn't to be," Wacha said. "But it was still a pretty special night."
Zimmerman hit a chopper just over the 6-foot-6 Wacha, and the ball bounced slowly toward shortstop. A charging Pete Kozma grabbed it with his bare hand and whipped a throw to first that was a little wide, pulling Matt Adams off the bag as Zimmerman arrived.
"I think it nicked off my glove a little bit," Wacha said.
As the ball left Zimmerman's bat, several Cardinals started to climb the dugout railing, ready to pour onto the field to celebrate. Second baseman Matt Carpenter did a little hop, all set for the final out.
But first base umpire Jeff Kellogg correctly called Zimmerman safe, and the Cardinals sagged right along with their fans.
"Pete made a heck of an effort," Wacha said. "The defense played great behind me. That's the only reason I was able to go that long. Everyone in the infield was making plays.
"It was just an unbelievable night."
Wacha (4-1) was pulled after Zimmerman's hit and walked off to a huge ovation. The right-hander struck out nine and walked two.
"It was fun to catch him," Yadier Molina said. "The no-hitter would have been a plus. I was hoping to get it, but it didn't happen."
Cardinals manager Mike Matheny was impressed with Wacha's late-inning poise.
"For a kid to do that against a lineup like that, at this point in the season, it's hard to get your head around it," Matheny said.
But on the next pitch, Zimmerman spoiled it -- and joked that he used his "blazing speed" to beat out his 14th infield hit of the season.
"He pitched great. He really had his stuff going," Zimmerman said.
Texas' Yu Darvish lost a perfect game with two outs in the ninth inning against Houston on April 2 and San Francisco's Yusmeiro Petit had his try at perfection end one out shy against Arizona on Sept 6.
It has been 30 years since there was a no-hitter in St. Louis. Bob Forsch finished off his second for the Cardinals on Sept. 26, 1983, against Montreal.
Drafted 19th overall out of Texas A&M last year, Wacha has been up and down from the minors a couple of times this season. But he came up big for the Cardinals in the final week as they try to nail down their first division title since 2009.
St. Louis, which already clinched a playoff berth, maintained its two-game lead over Pittsburgh, which beat the Chicago Cubs 8-2. Cincinnati lost to the New York Mets 4-2, falling three games back with four to play.
The Cardinals have won four of five. They remained a half-game behind Atlanta for the best record in the NL.
Washington was eliminated from playoff contention with a 4-3 loss to St. Louis on Monday night.
Wacha retired his first 14 batters before Adam LaRoche reached on an error by Carpenter.
Span tried to break up the no-hitter with a two-out bunt in the sixth. The ball rolled just foul near third base, and the crowd booed lustily.
Robinson drove in Carpenter with a two-out single off Gio Gonzalez (11-8) in the third. Carpenter began the rally with his major league-leading 55th double.
Molina pushed the lead to 2-0 with a run-scoring double in the fourth.
Wacha was seeking the 11th no-hitter in Cardinals history. ... Nationals RHP Jordan Zimmermann (19-7, 3.18 ERA) gets his last scheduled shot at 20 wins on Wednesday when he faces RHP Shelby Miller (14-9, 3.12) in the finale of the three-game series. ... The Cardinals are 14-2 against NL East opponents at home.