The Jackets are winners of four straight; the Blues have the best record in the league and have won three straight. The Jackets are down several guys, including Derek MacKenzie, Derek Dorsett, Steve Mason, and Fedor Tyutin. Dane Byers and Allen York have been recalled to fill out the roster.
These clubs will play another game tomorrow, and all told will play three times in the span of 22 days. The Jackets have been playing spoiler over their last four, denying points to the Coyotes (twice), Avalanche, and Kings. The Blues don't technically need points to get into the playoffs, but they are currently holding on to the conference (and league) lead. Home ice would be huge for them, considering they've lost just four times in regulation in St. Louis.
In short, there is plenty to play for for the Blues.
Not to mention, these teams just do not like each other. At all. Ever.