Tampa Bay Lightning coach Jon Cooper watched his team defeat the Florida Panthers 6-2 to take a 3-1 series lead in Game 4 on Saturday. But he also saw two key players, star winger Nikita Kucherov and defenseman Mikhail Sergachev, leave in the third period with injuries at the hands of Florida players.

"The hockey game ended halfway through the second. It turned into something much different," Cooper said.

Kucherov left with 9:03 remaining after taking a slash on the leg from Panthers forward Anthony Duclair, who was given a minor penalty.

"When you see him go down, and he stays down, it's very concerning. Guys on our team aren't going to stay down unless they're actually hurt," Lightning forward Alex Killorn said.

With 3:36 remaining, Sergachev was sent hard into the boards by forward Patric Hornqvist as he released a pass in his own zone. Hornqvist wasn't penalized for the hit, but received a matching misconduct penalty with Tampa Bay's Pat Maroon.

When asked if he had an update on his injured players' status, Cooper said: "Nothing. Next question."

In total, there were 68 combined penalty minutes in the third period, which the Lightning entered with a 5-2 lead.

"We had to weather our emotions. There's no doubt. When our players are being told [by the officials] 'don't do anything stupid. We're gonna get you,' and the other team is getting rewarded for it? I just don't get it. It's just frustrating. People are coming to watch a really intense, good hockey game, and liberties are being taken," Cooper said.

"Don't get me wrong. We're not angels out there. I'm not sitting there and saying that. Far from it. But when there's a standard set and we're being told things are going to called, and when it doesn't get [called], there's just confusion."

Cooper said he understood the dynamic of "message sending" from a team trailing in the series in a playoff blowout.

"There's nothing wrong with message-sending and tone-setting. That's part of the game. That's why we love it. That's why people are lined up for tickets. It's awesome. But do it in the parameters of the game, and the guys in stripes ought to control that. If it's not controlled, stuff like this happens like tonight [where] you have superstars lying on the ice," he said. "But you want that in the game. You want passion. There's so much great about it. You want passion, but now you're skewed on what you're allowed to do and what you're not allowed to do, and it keeps -- it just could be frustrating."

Game 5 is Monday in Sunrise, Florida, as the Panthers attempt to avoid elimination. While the Lightning face injury drama, the Panthers face goaltending drama with the season on the line. Sergei Bobrovsky made just nine saves on 14 shots before being replaced in the second period by Chris Driedger, whom Bobrovsky replaced in Game 3.

Waiting in the wings is Spencer Knight, 20, the 2019 first-round pick who was 4-0-0 in his last appearances, all in the regular season for the Panthers.