A game removed from scoring the 100th goal of his NHL career, Aaron Ekblad opened the scoring for the Panthers when he turned and fired a shot past Thomas Greiss from inside the bottom of the left circle to make it 1-0 just 1:20 after the puck had dropped in the first period.
Jumpstarting the scoring sequence, Gustav Forsling made an excellent play in the defensive zone to break up a cross-ice pass with his stick and send the action the other way up the ice.
Doubling the lead less than two minutes after Ekblad broke the ice, Gudas fired a shot from just below the blue line that snuck past Greiss and into the cage to make it 2-0 at 2:58.
Netting his team-leading 12th goal of the season, Carter Verhaeghe extended the lead even further when he collected a pass from Sam Reinhart, dashed past a pair of defenders and beat Greiss on a breakaway to make it 3-0 at 8:47.
Getting the Blues on the board, Brandon Saad followed up on a shot from Josh Leivo and fired the ensuing rebound past Spencer Knight from on top of the blue paint to make it 3-1 at 11:39.
Heading into the first intermission, Florida led 14-5 in scoring chances.
"That's our game at its best," Panthers forward Anton Lundell said of the period. "It's something we need to try to do the whole game."
Not taking their foot off the gas, the Panthers added another goal in the second period when -- a split second after killing off a power play for the Blues -- Lundell took a pass from Reinhart on a 2-on-1 break and roofed a shot into the top of the cage to make it 4-1 at 12:50.
Taking advantage of an awkward bounce behind Florida's net, Ryan O'Reilly grabbed the puck and tucked a shot into the net to trim St. Louis' deficit down to 4-2 at 8:16 of the third period. At 13:43, Jordan Kyrou brought the Blues back to within one goal when he made it 4-3 with a top-shelf snipe.
"We had a bad break on the second goal," Panthers head coach Paul Maurice said. "It came off the middle post behind the net and came back out. Spencer was right. He thought the puck was going to the other side of the net. He didn't make a mistake on that. He didn't get caught on the wrong side. He was right on that."
With 3:49 left in regulation, Vladimir Tarasenko scored to make it 4-4.
At 1:08 of overtime, Kyrou collected a stretch pass from Torey Krug and beat Knight on a breakaway to complete the comeback for the Blues and lock in the 5-4 win.
"I thought we played a very good two periods," Gudas said. "It's a pretty good team on the other side, too. They got some bounces and good breaks. I think our mistakes showed up in a big way today. It's just unfortunate the way the game went. I really thought we had a good start, good second. I thought in the third it got away from us."
