Joel Quenneville remembers years past when NHL teams leading going into the third period could feel comfortable chalking up two points. A win was a pretty sure bet.

Earlier this season, his Florida Panthers erased a four-goal deficit to win a game. And then they did it again. Even the three-time Stanley Cup-winning coach didn’t see that coming.

”We didn’t envision coming back either game,” Quenneville said.

It’s becoming easier than ever to envision. There have already been five four-goal comeback wins this season, tied for the most in NHL history. And the 18 three-goal comebacks are the most through the same number of games in 30 years.

No lead is safe.

”Used to be the dreaded, two-goal lead is the most dangerous in hockey, but now it seems like the four-goal lead’s the hardest one to hold on to,” Tampa Bay Lightning coach Jon Cooper said. ”Teams believe they can come back at any time.”

Coaches and players point to a number of different factors for all the rallying going on, ranging from rules designed to create more offense to better power plays, more skill and talent, and human nature when it comes to holding a comfortable lead or facing a difficult deficit.

”It’s very difficult to hold leads now just with some of the rules that have been added,” said coach Todd Reirden, whose Washington Capitals recently erased a three-goal deficit to beat the New York Islanders. ”Just different little nuances that have helped scoring increase in the league. It’s just the way that penalties are called, too, and the league wants offense and they love that aspect of teams coming from behind like that.”

Those rules include more penalties called for obstructing, hooking, holding and slashing and increased advantages on faceoffs for the offensive team. Just like the standings that are set up to be neck-and-neck down the stretch to the playoffs, the modern game is designed for no team to be out of a game.

When David Quinn’s New York Rangers went down 4-0 at Montreal this season, the second-year coach considered it a little unfair based on their effort. They won 6-5 in regulation.

”One of the things we talked about in between the first and second period was: ‘Don’t play the score. If you do the right thing over and over again, the game will reward you,”’ Quinn recalled. ”And I thought that’s what happened. Within a game, you’ve got to be mentally tough, and you’re going to have to have resiliency.”

See the Panthers, who stunned Anaheim and Boston with those four-goal comebacks. Quenneville has been behind an NHL bench for a long time and doesn’t have a scientific explanation for this phenomenon.

”You get a fortunate break on a bounce here, and it can really shift the momentum,” Quenneville said. ”There’s been a lot of offense in this year’s game, teams going for it. You’ve got a 4-0 lead, whether you take your foot off the pedal and all of a sudden you maybe relax a little bit, but the other team’s pressing, they’re pinching, they’re taking more offensive zone chances and thinking that way. You get a couple of breaks and all of a sudden, the other team’s on their heels.”

Much of it is psychological. Players after building a big lead could naturally think their heavy lifting is over for the game. Those on the other side are just getting started.

”The team that’s ahead, as much as you fight it, there’s a natural instinct to just ease off the gas a little and give (up) opportunities,” said Matt Niskanen, whose Philadelphia Flyers recently beat the Bruins in a shootout after trailing by three goals. ”Mentally, you tell yourself, ‘Don’t let up, keep playing the same way because we’re having success for a reason.’ It’s a really hard thing to fight.”

After reaching Game 7 of the Stanley Cup Final, the Bruins lead the Atlantic Division at the All-Star break despite a penchant for blowing leads.

”We’ve got to bear down,” Boston center Patrice Bergeron said. ”You can’t just have a good effort, be satisfied with that, and then just play for a half a game.”

Half a game isn’t enough, especially since hockey has moved toward more offensively skilled players and away from those tasked with keeping the puck out of the net. There’s also the fact that 25 of 31 teams are either in or within 10 points of a playoff spot, and it’s hard for teams to dominate a whole game — let alone a season.

”It just shows the parity of the league and that on any given night, everybody can beat somebody else” Reirden said ”It’s extremely competitive.”