Duncan Keith scored the winning goal on the power play with 8.5 seconds remaining, capping Chicago's rally from down 3-1. The defenseman beat goalie Jake Allen with a one-timer from the top of the right face-off circle off a pass from Alex DeBrincat, who tied the game 3-3 at 8:30 of the third.
"Well, I think we know that, the importance of their points for them," Keith said of the Blues. "Yeah, I think there's something to be said for trying to play for that in some ways, but we're trying to win the game. You know, at the end of the day, it's a bigger game for them, but I thought that we did a good job of kind of matching that intensity, and for us it's just more fun to play in a game like that, more than anything. We haven't played in those situations where we're really playing for much at this point."
WATCH: [All Blackhawks vs. Blues highlights]
The Blues (43-31-6) remain one point behind the Colorado Avalanche for the second wild card into the Stanley Cup Playoffs from the West. Each team has two games remaining.
"It's tough to not sit here and talk about winning the game, that's for sure, and I think it's even tougher to say that we just didn't play well enough, especially when the game was on the line in the third period to deserve the win," St. Louis coach Mike Yeo said. "Nerves and bad decisions, a combination maybe of both, but I felt that we were a little bit tight in the third period, we weren't as aggressive as far as our checking game, but the puck decisions that we made were very poor and just let them ramp it up and let them get momentum, and obviously the more that we did that, the more it put us on our heels."
With the St. Louis loss, the Los Angeles Kings clinched a playoff berth.