SAN JOSE -- Logan Couture considered the start, "OK."
The San Jose Sharks, 7-3 at home in the Stanley Cup Playoffs, had ample energy and were inches from an early lead when forward Evander Kane's shot hit the goal post 12 seconds into Game 5 of the Western Conference Final against the St. Louis Blues at SAP Center on Sunday.
But a decent start devolved into a bad second period and an even worse third for the Sharks in a 5-0 loss. The Blues have a 3-2 lead in the best-of-7 series, which shifts back to St. Louis for Game 6 at Enterprise Center on Tuesday (8 p.m. ET; NBCSN, CBC, TVAS).
[RELATED: Complete Sharks vs. Blues series coverage]
The Sharks also have injury concerns; forward Joe Pavelski was injured on his first shift of the third period after a hit along the boards from Blues defenseman Alex Pietrangelo. Forward Tomas Hertl, who took a high hit from Blues forward Ivan Barbashev in the first period, did not play in the third.
Defenseman Erik Karlsson, who did not play the final seven minutes of the second period, did not return for the third. Karlsson also looked to be struggling in the Sharks' 2-1 loss in Game 4 at St. Louis on Friday.
DeBoer did not have an update on any of the injured players.
"It's easy to sit here and say now, yeah, sure you have regrets," DeBoer said of playing Karlsson on Sunday. "I mean, hindsight's 20/20, you know? We make those decisions based on reports we get form the player and medical, and the report was he felt he could play and get through the game."
The Sharks were fine with their first period, despite trailing 1-0 on Blues forward Oskar Sundqvist's fourth goal of the Stanley Cup Playoffs. They had another great scoring chance when defenseman Marc-Edouard Vlasic's shot went off Kane and the post 2:44 into the period. Twenty-one seconds later, Blues forward Jaden Schwartz scored his first of three goals off a rebound of Vladimir Tarasenko's shot for a 2-0 lead.
Video: STL@SJS, Gm5: DeBoer discusses 5-0 loss to Blues
"Lots of different twists and turns in that game," Kane said. "That type of stuff, it happens. It's all about how we respond."
But the Sharks didn't respond well. The Blues outshot them 20-6 in the second period, and Tarasenko scored on a penalty shot for a 3-0 lead at 6:53.
"We were kind of turning some pucks over and anytime you do that this time of year, the other teams usually feed off of that," Sharks defenseman Brenden Dillon said. "Whether it was plays to the middle or just not getting puck out of our zone … their [defensemen] are pretty active, which we like to be as well. We knew that coming into it. I think it was just a matter of execution."
It only got worse in the third when the Sharks were without Pavelski, Hertl and Karlsson and took eight penalties.
"You can't win or come back when you're in the box all period," Couture said. "It got away from us at the end. I would have really liked us to control our emotions and at least give ourselves a chance."
The Sharks are used to facing elimination; they trailed 3-1 in the first round against the Vegas Golden Knights and won back-to-back games against the Colorado Avalanche in the second round after being down 3-2.
But they squandered their chance to take a 3-2 series lead Sunday.
"We had a couple chances on the power play (0-for-2) to kind of get some traction and some looks," Dillon said. "But I think at the end of the day, we need to kind of ramp up our level instead of go the other way."