The Predators scored twice in 28 seconds when Forsberg gave them a 1-0 lead at 6:57 of the first period on a loose puck near the goal line Hofer thought he had covered up but didn't, and Yakov Trenin made it 2-0 at 7:25 off a 3-on-1 that Hofer inadvertently kicked into his own net. A video review confirmed that the puck had completed crossed the goal line.
Evangelista made it 3-0 at 13:53 when a pass caromed off a skate in the slot to him at the side of the net.
"I think we just got to be mentally tougher," St. Louis defenseman Justin Faulk said. "It's going to happen. We can't, if we get scored on first or second too, make us change our game. The game plan stays the same. It has to. We have to play out the whole 60 minutes. Leads change all the time. It is what it is. Stats probably say the team that scores first has the better chance, but it's not every night and you've got to just buy in and go, play a hard game."
Buchnevich cut it to 3-1 at 16:32 scoring off a pass from Marco Scandella.
Spencer Stastney's first NHL goal made it 4-1 at 2:45 of the second period on a wrist shot from the slot. Hofer was pulled after the goal.
"One of my earliest games I saw was the [Blackhawks] playing the Blues here and I was thinking about that before the game," Stastney said. "To score out here now is pretty cool.
"I had a tough gap. The puck just rolled around the boards. I joined. Evangelista made a great pass. I shot from the point. I don't know if that's going to go in on my stick all the time, but today it did. I feel fortunate."
O'Reilly scored on a 5-on-3 power-play at 4:46 for a 5-1 lead on a backdoor tap-in.
"Scoring the goal, yeah, that felt great," O'Reilly said. "... It was an unbelievable play by Filip to hit me backdoor. When you score against your old team, it always feels good."
Evangelista made it 6-1 at 6:00 on a second attempt from the slot after his initial shot was blocked.
Thomas cut it to 6-2 at 10:17 with a wrist shot from the left circle.
Forsberg gave Nashville a 7-2 lead at 17:29 on a quick shot from the slot, his ninth goal in seven games.
Jake Neighbours scored St. Louis' first power-play goal at home this season when he tipped in Torey Krug's point shot at 5:23 of the third period to make it 7-3. The Blues had been 0-for-18 at home with the man-advantage.
Sherwood scored to make it 8-3 at 12:42.
"It's obviously a way better feeling," Evangelista said. "Just showing up at the rink in times of the slump versus now, it's night and day. We're having a ton of fun. We're looking to stay hot."
NOTES: Forsberg has 38 points (17 goals, 21 assists) in 36 games against the Blues. ... O'Reilly has seven points (three goals, four assists) in a six-game point streak; he had 269 points (97 goals, 172 assists) in 327 regular-season games for St. Louis. ... Predators forward Gustav Nyquist had an assist to give him nine points (one goal, eight assists) in a seven-game point streak. ... Thomas has 20 points (six goals, 14 assists) in 17 games against Nashville. ... Blues forward Brandon Saad had an assist in 15:14 of ice time in his 800th NHL game.