The new and more aggressive Islanders still have some work to do.

In his first game as an NHL head coach, Lane Lambert’s style was on display Thursday in the regular-season opener against the Panthers, and at times it looked to have the Islanders buzzing. But there were too many lapses and too few times when everything clicked in a 3-1 loss to the Panthers.

“Aggressive” was the buzzword during training camp, and that was on display from puck drop at UBS Arena. The Islanders clogged the blue line when the Panthers tried to break out of their zone. Their defensemen got up on the play. The objective did not seem to be to win 2-1, but to generate chances, score and force the opposition to chase the game — a position in which the Islanders found themselves all too often last season.

But the adjustment to that mindset still looked like a work in progress, and the Islanders still finished the night with just one goal, which came on the power play. The Islanders gave up more rushes in the wrong direction than they have in the past, and too often the Panthers found an open man in a dangerous position with a shooting lane in the offensive zone. As the early part of the season unfolds, that will be the trade-off with which Lambert contends.

On Thursday, he lost that trade-off, as the Islanders committed too many penalties and took their foot off the gas at key points.

There was a moment of hope early in the third period, when Noah Dobson, on the power play, ripped a shot past Sergei Bobrovsky to tie the score 1-1 at 3:13. But the momentum lasted all of 30 seconds, before Patric Hornqvist put the Panthers back up 2-1 on a wraparound attempt that Ilya Sorokin couldn’t get to in time.

“Obviously,” Lambert said, “that was a kick in the stomach.”

After a push from the Islanders at the tail end of the game, it turned out that lapse in concentration that let Hornqvist get to the net was the decisive moment.

The Panthers struck first at 12:45 of the second period, when Eetu Luostarinen deflected Radko Gudas’ shot past Sorokin, who was late to react. What had been an even game in the first period was already starting to tilt in Florida’s direction before that goal (the Islanders had required Jean-Gabriel Pageau to clear a puck off the goal line during a penalty kill earlier in the period), but things got more lopsided from there.

The Islanders displayed sloppiness at times, taking six penalties, one of which resulted in a four-on-four. Though they excelled on special teams, it was not ideal to spend 10 minutes of the game at five-on-four.

“That’s the problem when you’re taking penalties like that,” Lambert said, when asked about how well his penalty kill played. “We took five, spent 10 minutes killing. It takes certain people out of the game a little bit and it adds minutes to others.”

Matthew Tkachuk, Florida’s prize acquisition over the summer, did not make it onto the scoresheet until his empty-net goal made it 3-1 with barely a minute to play, but he consistently created issues for whatever defensive pair the Islanders threw at him — usually Alexander Romanov and Dobson. The Islanders lacked similar punch from any of their own forwards.

“I thought we moved the puck too slow at times,” Lambert said. “We went D to D instead of going quick up [the ice]. That allowed them to get into their structure.”

It’s far from the end of the world to lose on opening night, particularly against an opponent that has Stanley Cup aspirations, as the Panthers do. But the Islanders, whose next three opponents missed the playoffs last season, will be under pressure quickly. No one expects everything to be perfect immediately, and the promising moments Thursday were apparent.

The sense from Lambert and company was not that the Islanders struggled to play aggressively, but that they did not do so often enough.

“I think we can play a little quicker,” Dobson said. “Especially in the second period, we were bringing pucks back too much, we were playing a little too slow. I think when we played quick, we stayed on them, we saw the zone time we got. I think we can learn from things and get ready for Saturday.”