Lubomir Visnovsky of the New York Islanders is tended to...

Lubomir Visnovsky of the New York Islanders is tended to after suffering an injury in the second period after a hit for a charging penalty against Tom Wilson of the Washington Capitals during Game 4 of the Eastern Conference Quarterfinals at Nassau Coliseum on Tuesday, April 21, 2015. Credit: Jim McIsaac

In a sport animated by instinct and emotion, all of the Islanders' instincts and emotions told them to retaliate for the ferocious hit that leveled teammate Lubomir Visnovsky. Still, they held off. Each of them used his "upper body," which is the National Hockey League's code word for "head."

They will all have to keep playing that way for the rest of the series against the Capitals, no matter how much they would love to get back at Tom Wilson, recently back from his own concussion and fresh out of the penalty box. No matter how they feel about it -- and they feel strongly, what with Kyle Okposo calling Wilson "an idiot" -- they can't let him get into their heads.

Hits like that one and the aftermath represent the worst and the best of the Stanley Cup playoffs, depending on your point of view. The play was ruled illegal -- Wilson got two minutes for charging -- but the possibility that Visnovsky might never play again for the Islanders makes two minutes seem awfully small.

Unless you consider it a coincidence that Visnovsky, who has a concussion history, has been hit high and hard repeatedly in this series, you see why the NHL employs the silly practice of referring to every injury vaguely as either "upper body" or "lower body." There always is the chance that if an opponent knew someone's specific weak spot, he would accidentally (wink, wink) pummel him there.

Anyway, the passions on both sides are astir, heading into Game 5 Thursday night in Washington. At Capitals practice in Arlington, Virginia, on Wednesday, Wilson told reporters, that he was "gliding in" and that "I think everyone in the room felt it was fairly clean."

The Islanders, meanwhile, believed that he was gliding in the way Amtrak "glides" on the open track between stations, and his "fairly clean" was about as spotless as a bus stop men's room. John Tavares said, at Nassau Coliseum, "We could have easily hit a lot of guys like that too. But we stay within the rules and play the game the right way . . . It was just a complete target of a defenseless player."

All of that makes you very interested in what will happen tonight, which is the sort of anticipation that makes the NHL playoffs tingle.

Islanders fans had two words to describe the episode: "Dirty play." The Capitals had their own two words: "It worked."

Brooks Laich said as much in a radio interview. The Islanders had to go much of the game without a power-play specialist, and had to overtax their five remaining defensemen. Whether they could have won rather than losing, 2-1, in overtime is anyone's guess. But it didn't seem to hurt the Capitals at all.

The worst thing the Islanders can do now, though, is let it fester. The Capitals have a strong power play and the Islanders can't afford to feed it for the sake of blasting Wilson. "It's definitely a fine line," said Matt Martin, to whom Caps coach Barry Trotz likens to Wilson. "Emotions run pretty high in a hockey game and when you see one of your guys go down like that you get a little upset. But at the same time you've got to realize there's a lot at stake. You've got to stay with the task at hand."

Thomas Hickey was the first to do that. As Visnovsky's defense partner, he immediately shoved the much bigger Wilson. "Then I saw we were going to get a power play," Hickey said. "But it's so hard. With Lubo, we know his head issues. It just makes me sick to my stomach to see him hurt and not feeling good. Just concern, more than retribution."

If they feel it is necessary in hockey's checks and balances, the Islanders might find an occasion to take it up with Wilson one day. That day isn't today. As hard as it is, they have a game to win, not a score to settle.