Maybe it was their failure to capitalize on the few good scoring chances they generated. Maybe it was the penalty by Patrick Marleau that not only ended their own power play but also led to the winning goal.

But however you want to explain it, the Sharks now find themselves on the brink of elimination from the Stanley Cup playoffs after dropping a 2-1 decision to the St. Louis Blues on Thursday night at HP Pavilion.

"We weren't very opportunistic. We're not burying the chances we do get, and that's the difference tonight," defenseman Dan Boyle said. "Frustrating, yeah. But you get over it, you move on."

Moving on now takes the Sharks to St. Louis, where on Saturday at the Scottrade Center they'll try to stay alive in a series they now trail 3-1.

"I think there's going to be a team that comes back from 3-1 in these playoffs," coach Todd McLellan said. "There are a number of us that are at it, and it may as well be us."

The Blues grabbed an early lead on a first-period goal by B.J. Crombeen, but it was a third-period power-play goal by Andy McDonald with eight minutes left after an interference penalty to Marleau that ended up as the winner after Joe Thornton scored with 1:07 remaining.

But three minutes before Crombeen's goal at 7:12 off a pass from Patrik Berglund from behind the San Jose net, an outlet pass from Brent Burns sent Logan Couture in all alone on Blues netminder Brian Elliott, who extended his pad to block the scoring attempt.

"Just a good save by him," Couture said. "I wish I got another shot at it."

McLellan agreed with the suggestion that save could have changed the momentum of the entire game but mentioned other saves by Elliott on Marleau and Joe Pavelski as keys to the outcome.

"You have to cash in on the four or five real good opportunities that you get a night," the coach said. "If you don't, then you end up in the situation we're in."

After a scoreless second period, the Sharks were generating sustained pressure in the offensive zone and ended up going on the power play when Blues defenseman Barret Jackman cross-checked Brad Winchester.

But before the two minutes were up, Marleau was cited for interfering with St. Louis defenseman Kris Russell behind the San Jose net -- the kind of penalty that normally earns a coach's wrath for where it occurs on the ice.

"If somebody goes into the boards like that, they really have no choice but to call it," said Marleau, who didn't think he bumped Russell that hard. "You're hoping that they see it was just a little bump, but it is what it is."

McLellan didn't fault his forward, or the referee for making the call.

"He's charging into a pile looking for a loose puck and a guy steps in front of him and his momentum takes him through that player and knocks him down," the coach said. "Not malicious or ill intent there."

The winning goal came on the subsequent St. Louis power play when Antti Niemi stopped the initial shot by David Perron, only to have the puck bounce high in the air and land in the crease. There McDonald got his stick on it just ahead of Thornton, who was trying to clear the puck.

Overall, the Sharks saw the game as an improved effort, even if the results weren't there at the end.

"We're just snakebit for some reason," Thornton said. "But it is what it is, and now we have to win some games."

McLellan, too, thought it was his team's best showing in the series despite the fact the Sharks won Game 1 in overtime before dropping the next three.

"We didn't get what we wanted, yet I thought this was probably our best 60-minute effort in the series," the coach said. But "you can't take consolation in having a good game. Not in the playoffs. You've got to find ways to win."

For more on the Sharks, see David Pollak's Working the Corners blog at blogs.mercurynews.com/sharks.