Petr Cajanek had a goal and an assist for the Blues, who got a short-handed goal from Jamal Mayers to cap a four-goal second period. It was the first short-handed goal given up this season by the Ducks, who were the only team that hadn't allowed one.
Curtis Sanford finished with 30 saves after being staked to a 5-0 lead, ending Anaheim's five-game win streak against the Blues. Manny Legace got the night off after starting 15 consecutive games.
Doug Weight and Keith Tkachuk also scored for St. Louis.
Teemu Selanne and Corey Perry scored for the injury-plagued Ducks, who are 5-7-2 in their last 14 games after winning 10 of their previous 11. Anaheim captain Scott Niedermayer, trying to pick up the slack defensively until fellow Norris Trophy winner Chris Pronger returns from a broken foot that already has cost him seven games, was on the ice for all of St. Louis's goals - including Dallas Drake's short-handed score into an empty net with 3:38 to play.
The Blues, who missed the playoffs last season for the first time since 1979 and had the league's worst record, are 10-4-4 since Andy Murray replaced Mike Kitchen as coach Dec. 11. On Thursday night, Murray will return to Staples Center in Los Angeles for the first time since he was fired as Kings coach on March 31.
St. Louis scored on three of 14 shots against Ilya Bryzgalov, making his seventh straight start while Jean-Sebastien Giguere recovers from a groin injury.