The Blues' Jeff Woywitka celebrates with his teammates after scoring his first goal of the season during the first period Wednesday against the Blackhawks in Chicago.
Mason was not heavily tested in earning his 14th career shutout as the injury-depleted Blues limited Chicago's chances.
Cristobal Huet made 27 saves for Chicago, shut out at home for the first time since March 12, 2008. The Blackhawks have lost two straight games at United Center in regulation to drop to 14-4-5 at home.
Mason made one of his few tough saves just 2:45 into the first, stopping Andrew Ladd from the edge of the crease. The goalie needed to be alert during goalmouth scrums a few times in the second and third, but Chicago generated little sustained pressure.
The Blackhawks entered the game averaging 3.45 goals, but have scored just five in their last four.
The Blues entered the game with seven players on injured reserve, including forwards Paul Kariya and Andy McDonald and defenseman Eric Brewer and Erik Johnson.
Thanks to three power-play chances -- including a 5-minute advantage set up by a major penalty to Chicago's Cam Barker for a hit on David Backes -- the Blues outshot the Blackhawks 16-3 in the first period. However, they led only 1-0 after 20 minutes.
The Blues didn't beat Huet until Woywitka scored a power-play goal on their 16th shot with 1:55 left in the first. Woywitka's drive from the point slid over Huet's left pad and into the net.
Following a scoreless second, Chicago's Matt Walker poked a rebound of his own shot under Mason and into the net at 2:46 of the third. The goal was not allowed, however, because one of the referees had whistled the play dead when Mason covered the original shot with his pad.
Tkachuk made it 2-0 during a 4-on-4 at 7:28 of the third. From the edge of the crease, he stuffed a shot between Huet's pads.
A shot by Chicago's Martin Havlat hit the post at 10:33 of the third. Mason made a point-blank save on Dave Bolland during a Chicago power-play with 4:25 left.
Notes: Blackhawks D Duncan Keith sat out his fourth game with a
probable concussion. Keith, who leads the Blackhawks with just under 26 minutes of ice time per game, is out day-to-day. ... The Blackhawks honored former RW Tony Amonte in a pregame ceremony. Amonte spent nine of 16 NHL seasons with Chicago. ... St. Louis D Roman Polack missed his second game with a broken foot and LW Yan Stastny missed his fifth with thumb injury. They're the most recent additions to the Blues' IR list.