LAS VEGAS -- Vegas Golden Knights captain Mark Stone could be out for an extended period with an injury that coach Bruce Cassidy said Thursday wasn't related to his surgically repaired back.

Cassidy said Stone was week-to-week with an upper-body injury. He got hurt during Tuesday's 5-3 home loss to the Nashville Predators.

"I don't have an idea on his return date," Cassidy said. "The medical team will update us as we go along. We're going to miss him, obviously, but we've got to focus on the task at hand."

Stone leads the defending Stanley Cup champions with 53 points, including a team-high 37 assists.

"We can make up some of the offense as we go along," Cassidy said. "But if we play good defense with this team, generally it leads to good offense. That's what fuels our offensive game."

Stone had two back surgeries within 13 months, the second one sidelining him for the final stretch of last year's regular season. He returned in time for the playoffs, scoring three times in the Game 5 clincher against the Florida Panthers to claim the Cup.

The Knights entered Thursday night's game against the Toronto Maple Leafs in second place in the Pacific Division with 70 points, 10 behind the Vancouver Canucks. The Edmonton Oilers (68 points) and Los Angeles Kings (66) were right behind them in a tight playoff race.

If Vegas places Stone on long-term injured reserve, that could free up money for the often aggressive Knights to look to acquire players at the March 8 trade deadline.