SAN JOSE -- The San Jose Sharks were forced to play most of Game 5 of their Western Conference First Round series against the Los Angeles Kings on Saturday without star defenseman Marc-Edouard Vlasic, and he could miss Game 6, coach Todd McLellan said after his team's 3-0 loss.

Vlasic left the game with 5:51 remaining in the first period after being checked into the boards by Kings center Jarret Stoll, who received a minor penalty for roughing. Vlasic did not return to the game.

"He didn't return after the blow he took to the head from Stoll," McLellan said. "He's got an upper-body injury. You can call it that."

McLellan said the referees didn't explain why Stoll received only a two-minute minor.

"They have a tough job," McLellan said. "They can't determine the extent of an injury on the spot. I don't hold them accountable for that. They made the call that they thought was appropriate. Unfortunately he's injured. We want to get that out of the game if we can."

Vlasic has been one of the Sharks' most durable players; he's missed one game during the past three seasons. That came late this season when McLellan decided to give him a day off to rest for the upcoming Stanley Cup Playoffs.

Vlasic has played 600 regular-season games in his NHL career, which began in 2006-07 when he made the team as an 18-year-old. He has played in 84 career playoff games.

Vlasic was a key player for Canada's gold-medal winning team at the 2014 Sochi Olympics. A dominant possession player, he garnered attention for the Norris Trophy this season and is one the Sharks' top penalty killers and shot blockers. He entered Game 5 with a team-high nine blocked shots.

The Sharks, who trailed 2-0 when Vlasic left, played the rest of the game with five defensemen.

"Playing five D is not something you're used to," Sharks defenseman Dan Boyle said. "The problem was playing five D when you're down 3-0. That's where it gets a little bit difficult. Five D when you're up you can kind of keep it simple and play a certain way. But, you're down three goals, five d-men pushing the puck, rushing up, it definitely got a little difficult but I thought we handled it well."

If Vlasic can't play, Matt Irwin would be his likely replacement. Irwin played 62 games in the regular season and had two goals and 17 assists. He fell out of favor late in the season and has not made an appearance in the playoffs.

Last year in the playoffs, Vlasic played a handful of games despite a broken foot.