Pujols reached 30 home runs for the 11th consecutive season when the first baseman connected in the sixth inning off the Pittsburgh Pirates' Jeff Karstens. The NL home runs leader is the first player in major league history to hit 30 homers in each of his first 11 seasons.
Yet the milestone was rendered rather moot when Garrett Jones homered to lead off the bottom of the 11th inning to lead the Pirates to a 5-4 victory and drop the second-place Cardinals a season-worst seven games behind Milwaukee in the NL Central.
Pujols' 28 career home runs at PNC Park are his most at any visiting stadium.
"Those are just numbers. They just reflect how great he is," Cardinals manager Tony La Russa said. "But he is great. He's a real weapon. I can guarantee you, though, he's not happy right now because we lost."
The task of catching the Brewers seems to keep getting tougher each day as they have won 18 of their last 20 games. St. Louis was leading the division by ½ game before Milwaukee went on its tear.
"Right now, we need to win," said Cardinals starter Chris Carpenter, who struck out 10 in seven innings. "We had a chance to tonight and we didn't pull through. Right now, when you've got (39) games left and you have a chance to win a game, you need to win it and take advantage of that."
The win was just the Pirates' fifth in 21 games since falling out of first place in the NL Central and they trail Milwaukee by 13 games.
Jones' blast came on a 2-2 curveball from Arthur Rhodes (3-4) for his 14th home run. The homer was estimated at 440 feet as it carried over the right-field stands and bounced on one hop off a walkway and into the Allegheny River.
It was Jones' second career game-ending homer; he connected against San Francisco's Bob Howry on July 17, 2009. It was also just his second home run in 51 at-bats against left-handed pitching this season.
"Arthur Rhodes is always tough on lefties and I was just hoping I could get on base against him to start the inning," Jones said. "I was lucky that he hung a curveball there."
While Jones hit a mammoth homer, Pirates center fielder Andrew McCutchen's catch in the top of the 11th was just as impressive as he sprinted into the left-center field gap and made a backhanded grab of Pujols' drive for the final out. Rafael Furcal was running from first base on the pitch and could have scored easily if the ball got past McCutchen.
That capped a frustrating night for the St. Louis offense as it had 10 hits but stranded 11 runners thanks in large part to going 2 for 10 with runners in scoring position.
"It's a tough league. If you can't handle it, go home," La Russa said when asked about frustration. "Either you're going to break their hearts or they're going to break your heart. We'll tough it out and be ready tomorrow."
Chris Resop (4-4) pitched two scoreless innings for the win.
Pittsburgh tied the game in the ninth when Neil Walker homered on the first pitch from closer Fernando Salas, a rookie who blew his fourth save in 27 opportunities. Walker, who has 10 homers, had not connected at home since June 5.
St. Louis had gone ahead in the top of the ninth on Matt Holliday's sacrifice fly off closer Joel Hanrahan, snapping his streak of 15 consecutive scoreless innings.
Jon Jay led off the ninth with a double down the left-field line and was bunted to third by Furcal. Pujols was intentionally walked for the second straight plate appearance so Hanrahan could face Holliday, who briefly put the Cardinals ahead with his sacrifice fly.
Carpenter allowed three runs on five hits with one walk.
David Freese had three hits for the Cardinals and Jay added two.
Walker had three hits for the Pirates, McCutchen blasted a three-run home run and had two hits and Jose Tabata had two hits in his first game since he strained his left quadriceps on June 26. Jones also had two hits.
Karstens allowed three runs and six hits in 5 1-3 innings. He walked two and struck out five.
The Cardinals tied the score at 3-3 with a two-run sixth inning that chased Karstens.
Pujols led off the inning with his home run into the right-field stands. Lance Berkman singled one out later and scored on Freese's double to right.
Notes: Tabata was activated from the 15-day DL before the game and the Pirates optioned 3B Pedro Alvarez to Triple-A Indianapolis. Furcal and Jay flip-flopped places in the batting order with Jay hitting leadoff and Furcal hitting No. 2, a move La Russa hopes will help the Cardinals cut down on hitting into double plays. They lead the NL with 132. Pirates RHP Evan Meek, on the DL since June 8 with shoulder tendinits, is scheduled to throw a simulated game Thursday at the Pirates' training facility in Bradenton, Fla. If that goes well, he will begin a rehab assignment with Class A Bradenton next Monday. Cardinals RHP Kyle Lohse (10-7, 3.37) will start against LHP Paul Maholm (6-13, 3.60) on Wednesday in the finale of the three-game series. Lohse is 5-2 lifetime against Pittsburgh. Maholm has lost his last four decisions and Pujols is 21-for-36 (.583) against him with seven doubles and two home runs.