St. Louis scored two third-period goals, Niittymaki stopped 39 shots and the Lightning beat the Vancouver Canucks 3-1 on Tuesday night.
"He kept us in the game," St. Louis said. "Niitty made some big saves for us and I thought we came out strong and played some pretty good minutes in the third. We got some goals and we've been doing a good job playing with the lead in the third. Niitty, obviously, is the backbone of that."
Steven Stamkos added a goal and an assist for the Lightning, who have won four in a row for the first time since November 2007. Niittymaki improved to 7-0-1 over his last eight starts.
"He's definitely earning his keep," Tampa Bay coach Rich Tocchet said of Niittymaki. "We just keep getting great play from him."
St. Louis also had an assist and has a seven-game points streak (seven goals, four assists).
Vancouver got a goal from Ryan Kesler. The Canucks are 2-3 on the first leg of an NHL-record 14-game road trip.
"We played a pretty good game," Canucks left wing Daniel Sedin said. "It was a step in the right direction. When you're in a tough stretch like this, you've got to play good defensively and make the simple play."
Daniel and Henrik Sedin both have gone four games without scoring a goal, and have combined for just one assist over the stretch. Henrik Sedin had a shot hit the post in the first.
Tampa Bay took a 2-1 lead on St. Louis' short-handed goal from the slot at 2:52 of the third. It was just the second short-handed goal by the Lightning this season.
St. Louis scored his 20th goal to make it 3-1 with 4:20 remaining.
Stamkos put the Lightning up 1-0 with a power-play goal eight minutes into the first. The center has eight goals and eight assists during a 10-game points streak.
"We're playing great as a team right now," Stamkos said. "It feels good to contribute, especially this time of the year."
Kesler tied it at 1 during a power play with 6.3 seconds left in the second.
Niittymaki stopped a short-handed breakaway by Alexandre Burrows midway through the second.
"It took us close to 40 minutes to solve him and he shut the door in the third," Kesler said. "We had some real good chances. We just couldn't find a way to beat him."
"I thought that might have been a little turning point and we could come back and tie it," said Luongo, who made 16 saves.
The Canucks entered outscoring their opponents 71-40 in the third this season. ... The Lightning have won eight of 11. ... Vancouver RW Pavol Demitra has left the team to tend to a personal matter. ... Lightning C Jeff Halpern played in his 700th NHL game. ... Tampa Bay signed RW Mark Parrish to a one-year contract and assigned him to Norfolk of the AHL.