Raycroft robbed Guerin during a power play at about the four-minute mark of the third, recovering from a nice stop on a deflection by lunging to his left and gloving Guerin's shot that would've tied it at 2.
"He double-clutched and I got a chance to dive across," Raycroft said. "A couple of times a year you get lucky on a play like that."
Guerin, who leads the Blues with 21 goals, took his time before shooting. Just enough time for Raycroft.
"Sometimes you just try to have a little poise and bear down on ones like that because they almost seem too easy," Guerin said. "I got great wood on it. It's unfortunate because that would have been a big goal for us."
About a half-minute later, Raycroft stopped Barret Jackman from the slot after a Toronto turnover.
"Andrew was basically the difference in the game," right wing Jeff O'Neill said.
Alexei Ponikarovsky added a power-play goal for the Maple Leafs, who have won the first four games of a five-game trip and have won five in a row overall. Toronto has also won eight of nine on the road and made the most of only 15 shots against St. Louis.
Toronto, which entered ninth in the Eastern Conference, is 11-0-2 when getting a goal from Ponikarovsky, and 16-9-3 on the road. The last three victories have each been by one goal.
"That's been huge for us," Steen said. "Knowing (Raycroft) is so hot back there is giving us a lot of confidence."
Ryan Johnson scored for the Blues, who have lost four of five to dull the franchise's surge under new coach Andy Murray. St. Louis lost for the first time in five games against Eastern Conference opponents.
The teams met for the first time since Dec. 9, 2003, in Toronto, and for the first time in St. Louis since Nov. 9, 2002, due to the NHL's unbalanced schedule.
Steen hit both goal posts on a shot early in the first period, but got his 11th goal on a bad-angled shot that deflected off Legace's stick and between the pads for a 2-1 lead with 1:43 left in the second.
Blues defenseman Dennis Wideman broke his stick early in a prolonged possession for Toronto, and St. Louis missed a couple of other chances to clear the puck.
"The puck was about 2 inches from getting out about three times," Murray said. "The bottom line is it didn't get out."
Legace had expected another pass and the shot caught him leaning the wrong way.
"I picked off two passes right before that and thought he was going to pass it again because there were a couple of guys out front," Legace said. "Just stupid."
Toronto was held to three shots in the period, and none until the final 4:10.
The Blues' checking line had tied it at 12:38 on Johnson's seventh goal, and fifth in 10 games. Johnson sped past the Toronto defense and slipped a backhander between Raycroft's pads.
The Maple Leafs capitalized on the Blues' only penalty of the first period for Ponikarovsky's 14th goal when he tapped in his own rebound at 15:55. Toronto is 11-0-2 when Ponikarovsky scores.
- Blues F Martin Rucinsky left in the second period with a groin injury.
- Maple Leafs F Boyd Devereaux returned after missing three games with a sprained ankle.
- Raycroft made his 15th straight start and Legace has started eight of the last nine.