If getting routed at home wasn't bad enough, the Padres learned that ace Jake Peavy is headed to the 15-day disabled list with swelling in his pitching elbow. An MRI exam earlier Monday showed no structural damage.
San Diego general manager Kevin Towers vented after watching the Padres lose their third straight and for the 11th time in 15 games. The Padres (16-30) have the worst record in the major leagues.
"We're bad, no question about it," Towers said. "You can't say it's early in the season. It's up to these guys in the clubhouse. I'm certainly not going to watch this for four more months."
It was the third straight win for the Cardinals, who got to face Wil Ledezma instead of Peavy, who was scheduled to make the start until being scratched on Sunday. The four homers were the most in a game this year for the Cardinals, who tied their season high with 16 hits.
Pujols went 3-for-5, scored three runs and drove in two. It was his 22nd career multihomer game and his second this season. Pujols has 11 homers.
"There's nobody who is a better hitter than him in the big leagues," manager Tony La Russa said. "The more he's in play, the better chance we have."
Pujols' first homer was massive. He led off the fifth inning by hitting reliever Justin Germano's second pitch into the balcony on the fourth floor of the Western Metal Supply Co. building in Petco Park's left-field corner, 405 feet from home plate.
"I knew I hit it good," Pujols said. "I knew it was going to stay fair. I've been getting some pitches to hit. I have to take advantage of them."
He hit another towering shot leading off the eighth, this one into the seats in left-center on a full-count pitch from left-hander Sean Henn.
"Anytime he gets pitches to hit, he's going to do damage," Ludwick said. "Both of those balls were launched. When he gets on a roll, he's extremely dangerous. He's fun to watch."
Ludwick got some help from Padres left fielder Scott Hairston in hitting the first homer of the night, which gave St. Louis a 2-0 lead with two outs in the first.
Hairston positioned himself against the wall as he settled under the fly ball, but didn't get a good jump and the ball hit off the top of his glove and went over the fence. Skip Schumaker was aboard on a leadoff single.
"I'm not going to give it back," Ludwick said. "I'll take it. It was the luck thing. All you can do is put a good swing on it. You can't do anything after that. Fortunately for me it was a home run."
Hairston made a much better jump in going after Izturis' fly ball with one out in the fourth, but it left the park on its own to give St. Louis a 4-1 lead. It was Izturis' first.
Ludwick went 3-for-4 with three RBIs. He also hit a run-scoring double.
Starter Todd Wellemeyer (5-1) hit an RBI single and held the Padres to two runs in six innings. He walked three and struck out two.
Ledezma (0-1) gave up four runs and five hits in four innings, walked two and struck out two.
Peavy, the reigning NL Cy Young Award winner, had been scheduled to start but was scratched on Sunday due to soreness in his pitching elbow that had been bothering for three or four starts.
Padres officials checked Petco Park following an explosion Monday afternoon at a hotel under construction about 200 yards away. The ballpark wasn't damaged, but the blast was heard and felt by stadium workers and a handful of early arriving ballplayers and coaches. Authorities said 14 workers were injured, five critically. ... St. Louis' Rick Ankiel hit off a tee but is still listed as day-to-day with a sprained right shoulder. ... Cardinals LHP Mark Mulder is likely to resume his rehab from shoulder surgery in 10 to 14 days. He was pulled from a rehab assignment earlier this month due to a mild rotator cuff strain.