Kucherov slammed his right shoulder or collarbone into the post early in the first period and never returned. Coach Jon Cooper didn't have an update on Kucherov after the Lightning's 2-1 loss to the Chicago Blackhawks that puts them on the brink of elimination.
Cooper said Kucherov would be evaluated Saturday night and Sunday.
"I thought he was going to come back, and then I got word he wasn't coming back, so I don't know," Cooper said. "He's a big part of our offence. In a series where goals are at a premium, it's tough when you lose one of your guys."
Game 6 is Monday night in Chicago.
Cooper was forced to jumble his lines and couldn't lean on the super-productive "Triplets" line of Kucherov, Tyler Johnson and Ondrej Palat. The Lightning cycled players through and gave a bigger workload to Jonathan Drouin in his second game of the series.
But it's almost impossible to replace Kucherov, who came into the game second on Tampa Bay in scoring with 23 points on 10 goals and 12 assists.
"He contributes on the offensive side of the puck a ton," winger Ryan Callahan said. "I'm not going to hide it, he's a guy we missed tonight."
The Lightning will miss him more going to United Center trying to save their season. Kucherov had three assists the first time the Lightning faced elimination in Game 6 against Detroit.
"Obviously you hope he's OK," captain Steven Stamkos said. "He's a big player, clutch guy for us who has played extremely well to get us here. Whether he goes or not, we have guys capable of stepping up and we have no choice but to find a way."
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