Kucherov left the game with 6:05 remaining in the third period of Tampa Bay's eventual 6-2 victory over the Avalanche that cut Colorado's series lead to 2-1.
As the Lightning winger handled the puck, Toews stuck his stick in Kucherov's back and then pushed him along the ice and into the boards as Kucherov fell to one knee.
Kucherov got up and briefly went after Toews. He did come out for the ensuing power play after Toews was whistled for a cross-check, but then went to the Lightning trainers' room.
"It's one of those plays you don't want to see," said Lightning defenseman Victor Hedman. "It's a dangerous play. You never want to see that. We'll see if anything happens -- probably not. But it's a dangerous play."
The Toews cross-check happened around two minutes after Kucherov hit Avalanche defenseman Josh Manson along the end boards on a hit that could have warranted a penalty. Manson finished the game for Colorado.
Coach Jon Cooper said there was no update on Kucherov's status.
"No update on any of the players, unfortunately. We'll do that tomorrow," Cooper said.
As for the Toews cross-check, Cooper said the incident speaks for itself.
"When you get asked questions like that, you're looking for an answer that everybody in the building already knows," said Cooper. "It's a game. It's a contact game. But guys know what they're doing. Smart, savvy players know what they're doing with their stick. We all saw it."
Kucherov is the Lightning's leading postseason scorer with seven goals and 19 assists for 26 points in 20 games. He had two assists in the Game 3 win.