SUNRISE, Fla. -- Conor Sheary said he felt the Pittsburgh Penguins were in "vacation mode" during Friday night's first period, falling behind by two goals.

After that, though, the Penguins put away the beach towels and played more like the team they are -- the two-time defending Stanley Cup champions -- in rallying to beat the Florida Panthers 4-3 at the BB&T Center.

Playing with a man advantage, Sheary scored the go-ahead goal with 2:53 left as the Penguins finished 3 of 4 on their power play. Sidney Crosby and Evgeni Malkin scored Pittsburgh's other power-play goals.

Sheary's goal was set up by a brilliant pass from defenseman Olli Maatta.

"He can't do anything wrong right now," Sheary said of Maatta, who has six assists in eight games. "He's playing pretty (well). That was a great pass, saucer right on my stick."

With 4:24 left in the game, Florida's Radim Vrbata was sent off for tripping. And with time running out on the power play, Pittsburgh's second unit came through as Sheary was in alone and beat goalie James Reimer with a backhander.

"We talked about that before the game to use the weak side of the ice on the break in," Sheary said, "and I was just flying in with a lot of speed."

Sheary wasn't the only hero, though.

Malkin, who has three goals and seven assists this season, and Crosby, who has five goals and five assists, certainly made their presence felt as the Penguins (5-2-1) beat the Panthers (2-4-0) for the second time in one week.

Goalie Matthew Murray (28 saves), who had both wins against Florida, was strong after the first period.

Meanwhile, Panthers goalie Roberto Luongo left the game with 15:14 left in the third period after Sheary backed into him.

Luongo appeared to suffer a hand injury. He was replaced by Reimer, who stopped 11 of the 12 shots he faced.

"We will know more tomorrow," Panthers coach Bob Boughner said of Luongo's injury. "It's unfortunate -- he had made some big saves."

Florida's 2-0 lead, on two goals just 1:34 apart, didn't last long, but it was good for the Panthers while it lasted.

Jamie McGinn scored the first goal after Murray struggled to stop a bouncing puck. Murray swept the puck to his right, but McGinn swooped in, outskated two Penguins to the loose buck and beat the goalie stick-side.

Panthers star Aleksander Barkov, who has 49 goals the previous two seasons, got his first score of the season to make it 2-0. Barkov, set up at the bottom of the right circle, took a pass from Keith Yandle and beat Murray with a sharp-angled high wrist shot to his glove side.

"It was good that we had a lot of time left," Crosby said of Pittsburgh's deficit.

Indeed, just as Florida owned the first period, Pittsburgh dominated the second with three goals, including two by Malkin and Carter Rowney just 27 seconds apart.

On Malkin's goal, Phil Kessel threaded a pass and Pittsburgh scored just seven seconds into their power play. Kessel's pass, which went through a maze of defenders and deflected off Luongo's stick, made it an easy goal for Malkin, who tapped it in.

Rowney, who scored after the puck deflected off the skate of Florida's Michael Haley, tied the score 2-2. It was his first goal of the season.

Pittsburgh took the lead 3-2 with 11:12 expired in the second period as Crosby, parked on the doorstep, redirected a perfect pass from Malkin.

Florida defenseman MacKenzie Weegar tied the score 3-3 with 10:41 left in the third period, unloading a slap shot from above the right circle. It was Weegar's first NHL goal, and it came in his first game of the season and just the fourth of his career.

"This is the only time you'll see me smile after a loss," Weegar said. "I'm pretty happy to get my first goal."

The smiles didn't last long for Florida as Sheary's score proved decisive.

Boughner, though, said the reason his team lost was easy to decipher.

"It went sideways when we started taking penalties," he said. "We know they have one of the best power plays, and our (penaly kill) is struggling. It seems like everything that's coming at us is finding its way into the back of the net."

NOTES: Florida had three healthy scratches: D Ian McCoshen, C Denis Malgin and LW Connor Brickley. Malgin has yet to play this season, but this was the first absence for McCoshen and Brickley. ... Pittsburgh scratched Zach Trotman, C Scott Wilson and RW Josh Archibald. Trotman, though, may play soon. He was called up Thursday from AHL Wilkes-Barre to make up for the loss of D Matt Hunwick (concussion). ... RW Owen Tippett, Florida's first-round pick, was on the third line, playing his second game in a row. He had seven shots on goal in his NHL debut on Tuesday at the Philadelphia Flyers. ... Pittsburgh plays at the Tampa Bay Lightning on Saturday. Florida plays at the Washington Capitals on Saturday.