St. Louis has 21 wins this season, tying the total from last season, when the Blues finished with the league's worst record.
Rucinsky scored his 12th about six minutes into the game. He skated uncovered down the right side and took a cross-ice pass from Peter Sejna before slapping his shot left of goalie Marty Turco. It came on the Blues' second shot in the period.
Tkachuk got his 17th on a rare power-play goal midway through the third. Entering the game, the Blues had scored just once in 22 man-advantage opportunities. Doug Weight assisted on both goals.
The Stars forced Legace to make several brilliant stops. He snagged Mike Modano's shot about a minute into the third period after the Stars centre skated in on a one-on-one. Legace also made a glove save on Stu Barnes midway through the second period about six minutes before blocking Jeff Halpern's shot from just in front of the net.
If Legace wasn't stopping the Stars, they stopped themselves. They hit the post with a shot early in the game and Barnes had an open net but pushed the puck behind Legace and in front of the goal mouth midway through the first period.
Barnes put the puck in the net late in the game but it was waved off because Dallas had too many men on the ice.
Notes: C Ryan Johnson received a game-misconduct penalty after instigating a fight with Dallas R Krys Barch in the second period. ... Prior to the game, the Blues honoured Bill Guerin for playing in his 1,000th game Friday night in Detroit. He became one of 213 NHL players to reach the milestone.