After giving the Boston Bruins 14 power plays through the first three games of the series, resulting in six goals-against, the Blues went 2-for-2 on the penalty kill and tied the best-of-7 Cup Final with a 4-2 victory at Enterprise Center on Monday.
Game 5 is at Boston on Thursday (8 p.m. ET; NBC, CBC, SN, TVAS).
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"We wanted to make sure we were extremely disciplined," Blues defenseman Colton Parayko said after their first win at home in a Cup Final. "We came out, worked hard, worked for the puck and worked for the game. We wanted to make sure we weren't taking penalties that fed into their offense or fed into their game.
"Obviously, we understood how good their power play was last game, and we know how good it is and we were aware of that before the series."
In Game 3, a 7-2 loss for St. Louis, Boston went 4-for-4 on the power play on four shots on goal.