NEW YORK -- With a little help from their older teammates, the Florida Panthers' youngsters are adjusting quickly to the rigors of postseason hockey.

Now it is time for the fans of south Florida to find out again what happens when a best-of-seven turns into a best-of-three.

Alex Petrovic scored his first career playoff goal just before the midway point of the third period Wednesday night as the Panthers edged the New York Islanders 2-1 at Barclays Center.

The Panthers evened the best-of-seven series at two games apiece. Game 5 is scheduled for Friday night at BB&T Center in Sunrise, Fla.

"I thought it was 20 guys desperate to play a real good hockey game," Panthers coach Gerard Gallant said. "I thought our desperation was real good when the puck dropped."

The Panthers' desperation level might have increased following a frenetic second period. Both teams had goals disallowed within a two-minute span, and Florida's negated goal appeared as if it might be particularly costly when Jonathan Huberdeau's momentum on a breakaway carried him into Islanders goalie Thomas Greiss.

The puck, initially stopped by Greiss, trickled through as he was sent into the back of the net. Huberdeau had to be helped off the ice as the goal was reviewed in Toronto. Gallant then challenged the no-goal call, which also failed.

By that time, Huberdeau was already back on the Panthers' bench. The sequence continued a bizarre playoff debut for the 22-year-old Huberdeau, who was ruled offside on a goal that would have given Florida a 3-0 lead in what turned out to be a 4-3 overtime loss in Sunday's Game 3.

"On the spot, it hurt, but after that, I was fine," Huberdeau said. "I wish it would have been a goal."

The Panthers took the lead on a nifty power-play goal with 4:42 left in the second period. Forty-four-year-old Jaromir Jagr won a battle for the puck behind the Islanders' net and passed to 30-year-old Teddy Purcell, whose shot sailed under Greiss' glove.

However, the Islanders tied it with 15.3 seconds left in the period on a five-on-three goal by captain John Tavares.

"It's a tough one to give up late in the period like that, especially after we had taken the lead," Panthers goalie Roberto Luongo said. "But we stuck with it. We knew we were playing a good game as a team, and we just wanted to keep doing what we were doing."

Petrovic broke the tie with a slow-developing goal. The 24-year-old juggled the puck between the Stanley Cup playoffs logo and the faceoff circles before firing a shot that sailed to the right of a screened Greiss with 10:35 remaining.

"It's a lot of fun when you see your young kids playing the way they're playing," Gallant said. "Give a lot of credit to those older veteran guys, because they're really good for them."

Luongo (26 saves) survived a late flurry by the Islanders, who uncorked five shots in the final 3:03 and two in the final six seconds. Luongo gloved a shot by Brock Nelson as time expired.

"That's what the playoffs are all about," said the 37-year-old Luongo, a veteran of 66 playoff games. "Gotta gut it out. A lot of guys did a lot of good things tonight. Some huge blocks in the end. Gotta sacrifice the body. We've got a young team, but we're quickly realizing how hard it is to win."

The Panthers, who have home-ice advantage for just the third time in eight all-time playoff series, can now advance to the conference semifinals by winning twice more at home.

"Excited to see what the south Florida fans have going," said 23-year-old Panthers center Nick Bjugstad. "They were excited the first two games, so I can imagine they're going to be pumped for us when we come back."

Greiss made 27 saves for the Islanders, who missed a chance to take their first 3-1 series lead since 1993 -- the last season in which New York won a postseason series.

"You're not going to win many games when you score one goal," Islanders coach Jack Capuano said.

The top line of Tavares, Kyle Okposo and Frans Nielsen combined for 11 of New York's 27 shots. No other Islander had more than two shots.

"We've got one line creating all our offense right now," Capuano said. "We've got to find a way like we did in Florida when we had secondary scoring and then the other night when we had secondary scoring. If not, it's going to be tough."

NOTES: The Islanders scratched C Mikhail Grabovski (concussion), G Jaroslav Halak (lower body), C Anders Lee (broken leg) and D Brian Strait (upper body) as well as RW Steve Bernier, LW Eric Boulton, G Christopher Gibson, D Adam Pelech and D Marek Zidlicky. ... Islanders C John Tavares said Wednesday he missed a couple third-period shifts Sunday because he was getting hydrated. ... The Panthers scratched D Steven Kampfer (ankle) and C Vincent Trocheck (foot) as well as LW Quinton Howden, D Jakub Kindl and LW Shawn Thornton. ... Trocheck skated during the Panthers' practice Tuesday and following their morning skate Wednesday.