Home field is a truth universally acknowledged. But what's behind it?

Everybody knows intuitively (or because they have been told a million times) that playing at home gives teams an advantage. There are several reasons why this is generally true in the NFL, some of which carry a lot more weight than others.  

In the wake of all four home teams that won during Wild Card weekend now having to go on the road for the divisional round, here's a refresher course on what matters and what really doesn't in terms of playing at home is in order.

Crowd noise

Or lack thereof, as the case may be. The noise that a home crowd can generate when the opposing team is on offense is by far the biggest competitive advantage for the home team, because of its ability to eliminate the snap count advantage that the offense usually possesses. 

When the crowd is quiet, like they should be when the home team is on offense, every offensive player should have a split-second head start on their opponent on every play because they know the snap count and the defenders do not. That's huge. In a league where a split second -- especially off the snap of the ball -- can make a big difference, that advantage goes a long way for an offense's ability to move the ball down the field.  

There's a reason why initial quickness is such a highly desired physical trait in the NFL. The snap count advantage greatly enhances the impact of a player's initial quickness.

Plus, you can change up the snap count to your advantage to keep the defense off balance. You can do a "quick count" to try to catch them off guard or a "hard count" to potentially get the defense to jump off sides. Think about Aaron Rodgers and the Packers, who seemingly get 10-15 free yards and two or three "free plays" after the defender jumps offside every game. That's significant.

All those options go out the window when you are an away team in a noisy environment. Whether you have the guard signaling to the center to snap the ball or the quarterback attempting to clap to break the noise, the snap count edge is lost. Yes, you can do "silent two" when the ball is not snapped on the initial clap or signal for the guard, but rather on the second one -- to not allow defenders to just tee off on timing up the silent count -- but it is not the same. There's a reason why there are so many false start penalties for teams playing in Seattle, Kansas City and Arizona, just to name a few. It's tough.

I can distinctly recall it being so loud in a game I started against the Colts in the old RCA Dome that I felt like I had trouble thinking. It was deafening.

I remember it being so loud for a night game at Arrowhead Stadium in Kansas City when I played for the Buffalo Bills that I was thankful I was just backing up that night because that place was going crazy. Which leads me to the second advantage of playing at home …

Energy

While the noise is by far the most impactful advantage of playing at home, the vibe and energy that the crowd can emit is a very real thing. I'm not smart enough to understand the psychology around it or why it works, but I do know the crowd's intensity and passion helps fuel the players to give just a little bit more. It's a tough thing to explain if you've never really experienced it, but you can just feel it when you are playing at home and your crowd is really into it. It's awesome.

The flip side to that, however, is that sometimes when things aren't going well, the crowd's negative energy can have a bad impact on the team. Some guys respond to getting booed with renewed fervor, but others do not and it can just compound things.

With that said, the crowd's energy can also have an impact on the officiating -- not just the players -- especially in stadiums where the fans are seated closer to the field. A 2003 soccer study suggests that referees can get affected by the emotions of a raucus crowd, leading them to make a call or two in favor of the home team. 

Familiarity

The home team knows, or at least should, the playing conditions in their stadium better than anyone. And the familiarity factor is most important when it comes to a West Coast team traveling East: Those teams out West don't play as well the further East they travel

When I played for the Patriots, we used to practice on the game field all the time so that we would have a better feel for the grass (aka painted mud back then) than our opponents. That helped us know what footwear was ideal based on the time of year as well as what spots on the field had the most secure footing and which did not. Whether that was a huge advantage is debatable, but it was information and experience that we had and our opponents did not.

The familiarity component is especially important as it relates to both wind and the kicking game. Away teams think they know the wind patterns while on the road. Home teams know they do. 

There are potential negatives playing at home, however, including the distraction that may come with family and friends coming to town for the game and the stress that can sometimes come along with that. 

While that can be a factor at times, there's a reason why teams fight for home-field advantage just like there's a reason why the folks that set the betting lines in Nevada often peg the home-field advantage as being worth three points, give or take depending on what team and stadium we are talking about. No player injury, outside of a starting quarterback, would have such an impact on a betting line.

So now you know the biggest reasons, in order, why playing at home is an advantage.

All that said, there is one other reason why the home team wins often in the postseason: They are usually the better team. That's why they were seeded higher in the first place.