WASHINGTON - The pivotal fifth game of the Islanders' first-round playoff series with the Washington Capitals is on tap Thursday night.

On Wednesday, it was time for the Islanders to vent about Tom Wilson's big hit on Lubomir Visnovsky in Game 4 -- and for the Caps to brush it off.

Visnovsky is out indefinitely with a suspected concussion. The 38-year-old defenseman missed 58 games last season with a concussion, then took an accidental hit from Troy Brouwer in Game 3 that knocked him out of that game for a few minutes.

Wilson's hit was no accident, though. A source close to Visnovsky told Newsday that the Islanders are being cautious right now with their player; if he cannot return from this latest head issue, however, it's not a stretch to believe that the veteran's 14-year NHL career could be over.

"With Lubo, you know his head issues. It makes me sick to my stomach to see him hurt and not feeling good," Thomas Hickey told reporters after Isles practice Wednesday. "[Wilson] went in to hurt our guy, obviously."

"We have to stay disciplined," John Tavares said. "We could have easily hit some of their guys that way, but we stay within the rules and play the right way."

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Wilson told reporters following the Caps' practice at their facility in Virginia that he believed the hit was clean, though he was assessed a minor for charging. Caps coach Barry Trotz backed his player.

"He didn't leave his feet, he stayed low, puck's right there, all those things," Trotz said. "Tom Wilson didn't do anything other than run him over."

The Isles, already upset over losing Visnovsky, were further incensed when audio of Caps forward Brooks Laich's radio appearance on a Washington station surfaced on social media.

Laich went beyond defending Wilson. "What [the hit] did was Visnovsky got put out of the game and that puts them down to five 'D' in the second period," Laich said. "Playing with six defensemen is tough enough [against us], but playing with five is more difficult. So it's a quote-unquote good penalty to take."

The NHL's Player Safety department was informed of Laich's comments, though such things usually warrant only a talking-to, not a fine or suspension. Wilson did not hear from player safety regarding the hit, so he will be in the lineup for Game 5.

Visnovsky will not and that leaves the Islanders short two right-side defensemen, with Travis Hamonic still out. Rookie Griffin Reinhart will likely get the call after playing only eight games with the Isles this season.

Jack Capuano also strongly hinted at one change among his healthy forwards, saying "there's a good chance" Mikhail Grabovski would play for the first time since he suffered a concussion on Feb. 19.

"It's not a bad thing to get some fresh legs in there with the amount of games we have played," Capuano said. "We're going to make some changes, there is no question, with some of our line combinations and personnel."

Grabovski may go in at center in place of Brock Nelson, whose line with Anders Lee and Tyler Kennedy hasn't provided much the last two games.