David Perron made contact halfway up the shaft on a wrist shot by Pietrangelo from the point, and Backes altered the course of the puck again that beat Quick between the legs.
Quick shut out the Blues twice in the regular season and allowed eight goals on 172 shots in first round.
Voynov tied it at 16:58 as the Kings capitalized on a giveaway by defenseman Barret Jackman, who lost a battle for the puck with Penner. Elliott couldn't cover the ground in time after Penner's cross-ice feed as Voynov, whose eight goals tied for the NHL lead among rookie defensemen, scored his first point of the playoffs.
Elliott and Jaroslav Halak each shut out the Kings in the regular season, and the goal ended a dry spell of 1:47:47 since Willie Mitchell scored Nov. 22 in a 3-2 victory at St. Louis.
NOTES: Most of the St. Louis Cardinals attended the game hours after beating the Milwaukee Brewers, with reliever Kyle McClellan showing up clad in a Backes jersey. Shortstop Rafael Furcal and right fielder Carlos Beltran attended their first hockey game. ... The Kings have won six in a row on the road overall dating to last season.
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