Lars Eller saw his target. He quickly skated over to Boston Bruins forward Brad Marchand at the blue line and the two exchanged a shove. Eller immediately dropped a glove and grabbed Marchand’s collar. Marchand tried to skate away, but Eller held tight, dropped his other glove and continued tugging at Marchand’s collar even as a linesman stepped in between the two players.

Clearly Eller wanted to fight, but Marchand wanted no part it and the fight was broken up by a linesman. The entire incident left the Washington Capitals upset as they expressed after the game.

“I would rather fight him, but can't fight a guy that doesn't want to fight,” Eller said. “Everybody saw what he is. … I don’t think there’s a lot of integrity in his game.”

But why? Marchand did what most parents tell their children to do when presented with a fight. He walked away.  In so doing, he drew a minor penalty from Eller and gave his team a power play.

According to the fighting etiquette, however, Marchand was in the wrong.

Marchand forced a fight the last time these two players met on the Caps’ Opening Night and Eller felt jumped. Rather than stepping up to fight Eller and allowing them to settle their differences, Marchand refused thus breaking one of the many unwritten rules of fighting in hockey.

Hockey is the only professional sport in which fighting is allowed. Though technically against the rules, two players fighting on the ice will only net those players five minutes in the penalty box rather than a lengthy suspension.

But if fighting were just about raw emotion and trying to inflict physical damage on an opponent, it would quickly become distasteful. Hockey fighting is much more nuanced with a number of unwritten rules that govern the players’ actions. Those rules are constantly evolving over time.

“There's a million different ways that it can happen,” Tom Wilson said. “It's the No. 1 question that everyone always asks. How does a fight start? Why does a fight start? You just kind of have to be out there, feel it out and make a decision.”

Fighting used to be much more prevalent in the sport. It was valued to such a degree that players who could barely produce offensively and got very little playing time were felt to be a necessity in the lineup.

The days of the traditional enforcer, however, are over.

“The staged fights between guys that play under five minutes, that’s gone obviously,” Wilson said. “Probably a decade ago you would know before the game started that the two guys were going to fight. That's just the way it was, their tough guy vs. the other team's tough guy. That's gone now.”

In today’s NHL, the most common reason for fighting is to stand up for a teammate. Hockey is a contact sport so it is impossible to react after every hit, but if it is believed a player has crossed the line between physical and dirty, then he will have to answer for it.

“Probably all my fights are with a hit that I don't agree with at the time,” Devante Smith-Pelly said.

A very recent example came on Jan. 8 when Smith-Pelly dropped the gloves with Philadelphia Flyers defenseman Radko Gudas. Gudas delivered a shoulder check right to the chest of Nic Dowd that knocked Dowd to the ice.

Smith-Pelly’s reaction to the hit was immediate. If you see a teammate take a dirty play, then you are expected to respond.

“If you're right there and you're the first guy and you feel like that's what you should do, then you've got to do it,” Smith-Pelly said.

From the other end, if you deliver a big hit, you are not going to be caught off guard when the other team comes after you. It is expected and often respected even if it doesn’t happen right away.

“Sometimes you're almost doing the guy a favor,” Wilson said. “He asks [to fight] and you'd expect the same in return.”

As seen from Elle some grudges can carry over from a prior game. Wilson was suspended in the preseason for a hit he delivered to St. Louis Blues forward Oskar Sundqvist. When the Capitals played St. Louis in January for the first time since that hit, Wilson dropped the gloves with Blues defenseman Robert Bortuzzo in a fight that felt a lot more motivated by the Sundqvist hit than anything that was happening during the game. Wilson was engaged with another Blues player when Bortuzzo injected himself into the conversation and sparked a fight.

“In the St. Louis case, [Bortuzzo] wants to defend his teammate and you give him the opportunity to do so and if your teammate was ever hit, you'd expect him to be willing,” Wilson said.

While most fights may start with players standing up for teammates, hockey has not completely lost the old enforcer mentality. It has simply evolved.

That’s where players like Wilson come in.

The typical fourth line enforces of the past are gone as everyone is expected to produce in the current era of the sport, but teams also cannot be without someone willing to drop the gloves to defend his teammates.

And those players know who each other are.

“Before the game, you can look at a lineup and I know who on the other team would probably be willing to fight, who if something happened they would be ready,” Wilson said. “And then there's probably 11 other forwards that wouldn't. So when something happens, you go into Ottawa, you look at their lineup, it's a guy like [Mark Borowiecki], he's probably the guy that would fight if something happened. There's that understanding. I'm not going to go grab someone else on their team like the young [Brady Tkachuk] kid. There's just that understanding.”

But even if you know someone would be willing to fight, it doesn’t always mean that you should.

Wilson, for example, is typically on Washington’s top line and plays a major role on the team. Because of his growing role, Wilson cannot simply drop the gloves against anyone just because they ask.

“I try and really make sure the guys nowadays that I'm fighting have a role on the other team, that they're out there playing minutes,” Wilson said. “There's still guys like that around the league that are big parts of their teams that are willing to fight. If you get a five-minute major, you could be in the box for 10 minutes because you have to wait for a whistle. It can be a huge chunk of time so you've got to be really smart about it.”

That mentality reflects another modern change to fighting in that no one has to fight if they don’t want to.

In 1992, the NHL adjusted its rule on instigating a fight to make the punishment a game misconduct. In 1996, the league further changed the rule giving an instigator a two-minute minor, five-minute major and a 10-minute misconduct penalty.

The harsher punishment for a player deemed to be the aggressor has greatly changed the players’ mentality when it comes to fighting.

“It's just kind of the way it is now with the instigator,” Wilson said. “I can't go out and hold him accountable, he has to agree to it.”

But saying no to a fight is not without its risks. Refusing a fight when a player wants to stand up for a teammate or spark his team has its consequences.

Wilson said there have been players who told him after he refused a fight that they would continue targeting his teammates with big hits until he agreed. He then has to determine how much he will allow before he ultimately acquiesces.

“There's a line,” Wilson said. “If he's playing physical and the game's going well then [no], if he's hurting your guys then you've got to probably stand up for them. There's guys that take that approach.”

Even with the instigator penalty, you also still risk getting hit if you refuse a fight.

As much as the Caps hated how Marchand “jumped” Eller, they did acknowledge that Eller ultimately chose to drop the gloves rather than take the penalty. The problem wasn’t the fight, it was how Marchand started it.

“I chose to drop the gloves too because there sometimes comes a point where you just have to defend yourself,” Eller said. “I chose to do that in that moment.”

“For me, unless I really, really am mad, I don't think I would ever just pop a guy if he says no,” Smith-Pelly said. “At the same time, if someone's trying to fight me and I say no and he pops me, I can't really be mad.”

It can be difficult to understand at first why there are so many rules the players hold themselves to when it comes to fighting. In any other sport, there are no such understandings. Tensions rise, punches get thrown and an argument devolves into a fight and further into a brawl. When things get heated to a point in which emotions take over, things get very ugly very quickly.

But fighting in hockey is different because the underlying foundation in which all these unwritten rules are based on is respect.

In most cases when players want to fight they talk about it on the ice, drop the gloves so that no one gets the jump on the other, fight, then stop when one goes down or a referee gets in between them. There are even some instances where you see players give a sign of mutual respect after the fight.

And that’s why the Eller-Marchand situation felt so wrong.

In the home opener, Marchand was angered by Eller’s celebrating a goal in a 7-0 game and decided to fight him. Eller may not have wanted to fight, but he ultimately dropped the gloves. Having an issue with how Marchand started the fight, Eller wanted a chance to fight him in the rematch, but Marchand wouldn’t give him that opportunity. That’s the issue.

Eller didn’t want to fight, but he did. Marchand didn’t want to fight even when a player felt wronged, so he refused.

“When you get jumped like that, I was expecting [Marchand] to drop the gloves as well the next time so that was disappointing that he did not do that,” Eller said. “You would expect him to do that, that's kind of the code or the norm. The unwritten rule that he doesn't have to, but I think he should have and that would have been what most guys would have done.”

“That's usually how things are handled,” he added, “And both players acknowledge that this is how it's going to be handled and you're going to owe up to what you did. That was disappointing and not usually the way things go.”

According to the rule book, Eller was in the wrong and went to the penalty box as a result. According to the unwritten rules of the game, however, Marchand was wrong for not accepting the fight.

Fighting may not be as prevalent in hockey as it once was, but the rules that govern it are alive and well and ever-changing. Though it may not be as big a part of the game as in past years, fighting still remains deeply ingrained in the sport.

“It takes a certain breed,” Wilson said, “A certain guy to go out there on any given night and drop the gloves and fight so I think there's a respect level that, after that's done, you respect the guy.”