The Vegas Golden Knights suffered a 5-0 shutout loss to the Pittsburgh Penguins on Sunday at PPG Paints Arena, and the defeat was compounded by an upper-body injury to captain Mark Stone late in the first period.

Stone appeared to be injured on a routine check from Penguins defenseman Kris Letang. He immediately fell to his left knee, then skated slowly to the bench and down the tunnel. Coach Bruce Cassidy said Stone will travel with the team to Buffalo for Tuesday’s game against the Sabres, but no further update is expected until Monday.

“Upper body is all I was told, and we’ll see where that lands,” Cassidy said.

Stone, 33, has been the Knights’ most important player this season, recording 60 points in 43 games despite missing a month with a broken finger. His absence would be a significant blow as the team struggles for consistency.

The Knights (28-18-14) fell behind 4-0 after three second-period goals, including two on the power play. Goaltender Adin Hill allowed at least four goals for the second time in three starts since the Winter Olympics break. Penguins netminder Arturs Silovs made 22 saves for the shutout.

“We didn’t execute at our typical level,” Cassidy said.

The loss continues a troubling trend for the Knights, who have been outscored 9-1 in the first two periods over three games since returning from the Olympic break. They are 1-2 on their five-game road trip.

“If we had the answer, we wouldn’t be having poor starts almost every game,” winger Reilly Smith said. “We’re trailing too much, and it’s hard to come back in games in the third period every night.”

Center Jack Eichel, who won gold with Team USA, was held without a shot and was minus-2 for the second straight game. The five Knights who played in the gold medal game have combined for just one point since returning to the lineup Friday.

“It wasn’t a horrible first (period),” defenseman Brayden McNabb said. “(The) first 10 (minutes) were pretty good. Second period, they took it to us.”