Ottawa Senators coach Guy Boucher is sick of his team collapsing in the second period.

After a scoreless first period Vladimir Tarasenko, Alex Pietrangelo and Brayden Schenn all scored in the second period as the St. Louis Blues beat Ottawa 4-1, causing Boucher to vent.

"The second period, it's a disease. We stop shooting, we get perimeter play, we get east west play, complicated plays and you get the second period we had," Boucher said. "It's a disease we have to get rid of. We had the same disease last year to start the year and we got rid of it over time. It creeps back in.

"When we're at our best that's not who we are, and we lose games because of the second period. We've got to get rid of that disease."

Alexander Steen scored into an empty net at 18:42 to close out the scoring for St. Louis (28-17-3), while Carter Hutton made 20 saves.

Bobby Ryan replied for Ottawa (15-19-9) and Craig Anderson made 33 saves.

That disease was evident in an awful second period for the Senators when they were outshot 19-6 and, more importantly, outscored 3-1.

Tarasenko struck 6:13 into the period with a tip in front while spinning away from a Robert Bortuzzo point shot in front of Anderson.

The Blues took a 2-0 lead at 12:51 thanks to Anderson who, after making a save, batted the puck out of midair directly to Pietrangelo who had an empty net to shoot at from the left face-off circle. Thursday was Pietrangelo's 28th birthday.

"One, it's on your birthday, but two, it's finally nice to get back on the board about 4,000 shots later," said Pietrangelo. "I think we felt it coming, someone on the back end was going to score. Five-on-five we're really been jumping in the last two games here. It was just a matter of time before one of us got one."

Anderson could also be blamed for the Blues taking a 3-0 lead at 16:53 as he misplayed a backhand from Schenn and allowed the puck to pass through his legs.

The Senators got one of those back at 17:21 when Ryan's shot from 10-feet inside the blue-line redirected off the stick of Dmitrik Jaskin and over the shoulder of Hutton to cut the lead to 3-1.

The win was the second straight in Ontario for the Blues who were 2-1 overtime winners over the Toronto Maple Leafs on Tuesday. Ottawa was coming off its bye week and hadn't played in eight days.

"We got the first period we wanted. They were ready to go, they played hard and didn't give much to the opponent," said Boucher. "In the first period, we followed the plan. We played deep on them, we played 200-feet away from our goaltender and we shot.

"The first period was exactly what we wanted coming out of the break and then the second period."

The Senators also got defenceman Mark Borowiecki back into the lineup after he missed 22 games with a concussion. He delivered a big hit early, got into a fight and got his finger bitten by Kyle Brodziak during a scrum late in the second period.

"He did, but it's not a big deal. We were laughing about it afterward," Borowiecki said of the bite, also adding he was happy to be back in the lineup.

"I'm just trying to get back in the saddle there and do what I do best. I was so excited and I feel like I had some good jump. You feel kind of listless when you're away from the game for that long."

Ottawa forward Nate Thompson left the game and did not return with an undisclosed lower-body injury.

Notes- Fredrik Claesson and Jean-Gabriel Pageau were scratches for the Senators on Thursday, while Carl Gunnarsson, Scottie Upshall and Oskar Sundqvist were scratches for the Blues… The Senators haven't beaten the Blues in Ottawa since December 2013… The Blues have earned points in their last 11 games against Ottawa.