"We took our foot off the gas, and you can't do that against good teams," Backes said. "They took it to us. We made too many mistakes, and they put it in the back of the net. We got off our game plan and tried to be too cute in our end when they were putting pressure on us ... and the result was four unanswered goals in the third and another bad feeling in this locker room."
Jonathan Bernier made back-to-back starts for just the second time this season, but the Kings' backup goalie gave up three goals on eight shots in just over 21 minutes before getting pulled in favor of Jonathan Quick, who stopped five shots. Drew Doughty had two assists for the Kings, who haven't lost at home since Jan. 31.
Perron chased Bernier just 1:14 into the second period when he slipped unmarked into the slot and scored his eighth goal of the season. Stewart beat Quick at an awkward angle later in the period, but Voynov trimmed the Blues' lead to 4-2 with his second goal in 13 games.
The Kings then evened it with stunning swiftness. Richards scored his sixth goal of the season on his own rebound in the slot on a setup by Dustin Penner, and Muzzin quickly tied it in the first multigoal effort of his 29-game NHL career.
Carter chased Halak with a slap shot, scoring his ninth goal in eight games.
"Things started slipping, and when they tied it up, we started panicking," St. Louis forward Ryan Reaves said. "That seems to be what we've been doing a lot lately — hitting the panic button when things are going bad. We've got to keep sticking to our game plan and just keep grinding away."
NOTES: Pietrangelo's goal ended an 11-game goal drought. ... F Jason Arnott has skated for St. Louis in a few recent workouts, and the Blues are considering re-signing the 38-year-old veteran to bolster their flagging depth. ... The first period featured three fights and 40 penalty minutes, including Kyle Clifford's one-punch knockdown of Roman Polak with a nasty uppercut. ... Williams had three assists for the third time in his career — and the second time this season.