Tampa Bay Lightning captain Steven Stamkos missed his first game of the season Saturday against the New Jersey Devils. It was listed as an upper-body injury, but the exact nature of the injury was unknown.

Lightning general manger Steve Yzerman told reporters following the game that Stamkos has a blood clot in his arm. Yzerman said the pending unrestricted free agent is scheduled to undergo surgery Monday and could miss anywhere from 1-3 months.

“Obviously this situation is extremely disappointing because I wanted to help my team clinch a playoff spot and prepare for the start of the postseason,” Stamkos said in a statement released by the team. “During my recovery I will do all I can to help my teammates, and I hope to rejoin them soon in the Stanley Cup Playoffs.”

According to that same press release: “Stamkos is scheduled to undergo surgery to treat a type of Vascular Thoracic Outlet Syndrome (called Effort Thrombosis) near his right collarbone…The procedure is scheduled to be performed on Monday, April 4 by Dr. Karl Illig, Director of Vascular Surgery at Tampa General Hospital. Stamkos is expected to fully recover.”

The 26-year-old did not participate in his team’s practice Friday or Saturday’s morning skate. In 77 games, Stamkos has 36 goals and 64 points.

Yzerman said the team has no immediate plan to call anyone to fill in for Stamkos but mentioned Jonathan Drouin is a possibility.

Drouin has 11 goals in 17 games for the Syracuse Crunch in the AHL this season.

This isn’t the first time this season a member of the Lightning has dealt with a blood clot. Backup goalie Andrei Vasilevskiy missed the first month of the season after requiring surgery to remove a blood clot near his collarbone just like Stamkos.