Detroit halted a two-game skid with its second win in three tries against St. Louis this season.
The Blues, who beat Detroit 6-0 on Jan. 19, dropped their third in a row. They have lost three successive games in regulation for the first time since Feb. 27 to March 5, 2011.
Mrazek, recalled from Grand Rapids on Monday, stopped the first 14 shots he faced. Jimmy Howard, the team's No. 1 goalie, was given the night off after starting the first nine games of the season.