"They had to go with an emergency starter, and that gave us an edge," La Russa said. "We got to him early. We have to enjoy the moment."
The Braves, struggling to stay in contention in the NL East, lost their third straight game on the same day they placed Chipper Jones, who leads the majors with a .369 average, and Tim Hudson, their No. 1 starter, on the disabled list.
Morton (2-4), recalled from Triple-A Richmond because of Hudson's elbow injury, lasted only 3 2/3 innings. The right-hander gave up eight runs and seven hits, with his ERA climbing from 6.00 to 7.26.
"It's frustrating not to contribute and to do the exact opposite," Morton said. "That's the worst part of it. It kills me to know that I'm sitting here and I did what I just did. I know that every great pitcher has bad outings like this early in their careers, but it doesn't make it any better."
Looper (10-8) allowed two runs and seven hits in seven innings, winning for the first time since an 8-4 victory at Detroit on June 24. He entered with a 3-2 record and a 6.48 ERA in 25 games at Turner Field and promptly held the Braves scoreless through the first 5 1/3 innings.
"Atlanta has always hit me well over the last few years, so it doesn't hurt me for them not to have Chipper and [Brian] McCann in the lineup," Looper said. "With those guys in there, it's definitely not the same. They're All-Stars."
McCann sustained a mild concussion in a collision at home plate at Philadelphia on Sunday and is expected to miss three or four games.
Mather hit a two-run drive in the second inning for his third career homer, and St. Louis added four more runs in the third. The rookie outfielder had the first three-hit game of his career.
"Their pitcher wasn't necessarily bad," Mather said. "A lot of guys were swinging well."
Because of a throwing error by shortstop Yunel Escobar, three runners scored on Yadier Molina's two-run double. Pujols had already crossed the plate when Escobar took the cutoff throw and tried to get Troy Glaus at home.
Escobar's throw sailed past rookie catcher Clint Sammons. Glaus scored easily, and Molina, a slow-running catcher, also made it to extend the lead to 6-0.
"It's a better pitching staff than that. What's left of it," Braves manager Bobby Cox said. "[Jo-Jo] Reyes was not good yesterday. Morton was not good today. And you're not going to look good without starting pitching, simple as that. He missed his location way too many times and paid for it."
Braves left-hander Tom Glavine, out since June 11 with elbow inflammation, plans to throw 30 to 40 pitches in a simulated game on Wednesday. ... Cardinals center fielder Rick Ankiel missed his second straight game with a sore abdomen. La Russa doesn't know how long Ankiel will be out of the lineup, so the team recalled Nick Stavinoha from Triple-A Memphis. The club optioned reliever Mitchell Boggs to its top farm club to make room on the roster.