Lightning 'praying' Kucherov OK after leaving game with apparent injury
Kucherov made awkward contact with Capitals forward Garnet Hathaway and appeared to be in pain.
"We're praying he's OK," Stamkos added.
Tampa Bay head coach John Cooper didn't offer much of an update, but he said there was no need to hit the "panic button" yet.
"I have no way to answer what's going on with him. He'll be evaluated when we get back. He's a tough kid, so hopefully this isn't too bad. But again it's way too early to tell what's wrong," Cooper said, per NHL.com's Tom Gulitti.
The Lightning won the contest 2-1 thanks to Stamkos' heroics in overtime.
Kucherov has four points in three games so far this season.