After Stamkos tied it at 3 with 9:53 left with his second power-play goal of the game, Ryan O’Reilly beat the Senators to the puck behind the goal line and popped it out front to Stamkos, who batted it out of the air past goalie James Reimer.
O’Reilly set up the tying goal, too, firing a cross-crease feed to Stamkos with the man advantage. Nashville got the power play when Tim Stutzle cross-checked Stamkos.
“Took way too many penalties, especially in the third,” Senators head coach Travis Green said of his team’s late collapse. “Uncharacteristic of us to not at least get a point in a game like this. And I didn’t think we had enough players that played a strong game for 60 minutes.”
Predators captain Roman Josi, playing his 1,000th NHL game, also assisted on the tying goal. The defenceman is the 84th player in NHL history to play his first 1,000 regular-season games with one franchise.
Stamkos had his second hat trick of the season and 16th overall to push his season goals total to 24. Jonathan Marchessault also scored, and Cole Smith had an empty-netter. Juuse Saros made 23 saves to help Nashville end a three-game losing streak.
Stephen Halliday scored his first NHL goal, and Ridly Greig and Dylan Cozens added goals for Ottawa. Reimer, making his third straight start after signing with the Senators on Jan. 12, stopped 21 shots.
Ottawa closed a three-game trip. It had earned points in five straight games.
Halliday opened the scoring at 6:03 of the first period, knocking in a rebound. With David Perron out after surgery to repair a sports hernia, Halliday was recalled from Belleville of the AHL in the morning. He scored in his 19th NHL game, all this season.
Senators: Host Carolina on Saturday night to open a four-game homestand.
Predators: Host Utah on Saturday.
— With files from Sportsnet Staff