Wyatt Johnston scored twice, Jason Robertson had three assists and Tyler Seguin had a goal and an assist in his 900th NHL game for the Stars (46-21-14), who have won five straight and seven of eight. Scott Wedgewood made 16 saves.
"Everyone wants to feel good and confident scoring and feeling the puck and touching it, especially the power play, but I think you've got to stay in that neutral, humble, simple median and not get too ahead of ourselves, because the playoffs are a different demon," Robertson said. "Not going to get as much power plays, not going to get many looks and chances, so you've just got to bear down."
Robert Thomas had a goal and an assist for the Blues (37-37-7), who have lost two straight and had their home point streak end at six games (4-0-2). Joel Hofer, recalled from Springfield of the American Hockey League on Monday, made 32 saves in his eighth NHL start.
"We took some unnecessary penalties in the second period that cost us," St. Louis coach Craig Berube said. "They entered our zone too easily on their breakouts. They had too much time with the puck, that's the bottom line. Not enough pressure."
Johnston made it 1-0 at 5:49 of the first period when he chipped a puck in on the short side after Hofer couldn't corral an initial puck at the net by Stars defenseman Ryan Suter.