Bills vs. Chiefs proves once again that NFL overtime rules aren't as fair as college

    Tom Brady of the New England Patriots after his team's overtime victory over the Atlanta Falcons in Super Bowl LI in 2017. The Falcons offense never took the field in OT.

    (CNN)Millions of Americans tuned into one of the most epic NFL playoff games of all time Sunday. Buffalo Bills quarterback Josh Allen and Kansas City Chiefs quarterback Patrick Mahomes each led amazing last-second drives before a field goal forced the game into overtime.

    Once there, however, only Mahomes got to control the ball. Why?
    His team won the coin toss, received the ball and scored a touchdown. That meant the end of the game, and the end of Buffalo's season.
      Is that fair? A lot of fans believe that both teams should get the ball at least once in overtime like in college football. Indeed, a look at the statistics indicates that college football, especially in the playoffs, likely has a more equitable system for deciding overtime outcomes.
        The college system for overtime starts with a simple premise: Each team, regardless who wins the overtime coin toss, gets a chance to go on offense from the other team's 25 yard-line in the first overtime. (After the first overtime the rules do get somewhat more complicated.) 
        The team that wins the toss usually decides to go on defense first because they can know if the other team scored a touchdown or a field goal or failed to score. Based on that, the team that goes second can choose to be more or less aggressive when they get on offense. 
        It turns out, though, there hasn't been a statistical advantage to going second since 2013. According to data from Oklahoma State's Rick Wilson, a professor at the Spears School of Business, and my digging through box scores from Sports Reference, there have been nearly 300 overtime games involving Division I Football Bowl Subdivision teams from 2013-2021.
        The team that has received the ball second has won 49.7% of the time since 2013, or right about 50% of the time. In other words, there has not been an advantage to going second.   
        This year the statistics continue to show no advantage for the team that goes second. In fact, they have lost four more times than they have won in Sports Reference data. That's notable because the rules were adjusted this past season, if no team leads after the first overtime. (Read here for more on that rule change.)
        It's tough to be fairer than 50/50 in overtime. Yet, there have been some people in the past who argued that the college system isn't as fair as these stats make it out to be. You can see this in a widely shared tweet from former NFL player and now analyst Ross Tucker, this Ringer article from 2017, and a fairly cited Reddit thread on the fairness of the college overtime system. 
        I actually agreed with these folks before I looked at the most recent data. What seems to have happened is that there may have been a slight advantage to going second in earlier data.  
        Indeed, the Ringer article cited a paper co-written by Wilson, who has written numerous times on the college overtime system, that showed the team who got the ball second won about 55% of the time from 1995 to 2006. The co-authors of that paper noted, however, that the sample size was small enough for this difference to barely be statistically significant. 
        Wilson in an email told me that "there is no statistical significant difference (i.e. advantage) to choosing to go on defense first in college football OT." A better predictor of whether you win or lose in overtime is whether you have the more talented team.  
        The NFL system is quite different. A team can win the overtime coin toss, receive the opening kickoff and win with a touchdown without the other team getting an offensive possession. If the receiving team does not score a touchdown on its first possession (or if the kicking team does not score a touchdown on a turnover), the game continues.
        The current system (where you can't win with a field goal on the opening possession of overtime) has been in place since 2011 for the playoffs and 2012 for the regular season.  
        Confetti falls after the Patriots defeat the Falcons 34-28 in ovetime during Super Bowl LI at NRG Stadium on February 5, 2017 in Houston, Texas.
        According to the Stathead database, there have been over 160 overtime games under the current rules for winning in overtime (including the postseason). The team that got the ball first has won 52% of the time. The team that kicked off has won 41% of the time. The rest were ties, which happens in regular season games when no one scores during the now 10 minute overtime period.
        In other words, there has been about an 11 percentage point advantage in getting the ball first in the current NFL overtime system. Since 2017, when the overtime period was shrunk to 10 minutes in the regular season, the advantage in regular season games has been about 15 percentage points (54% to 39%).
        To be clear, the advantage of the team that gets the ball first in NFL overtime isn't dominating. I was surprised by how small it is. If you were to run statistical tests, it's right on the edge of statistical significance.  
        FiveThirtyEight's Neil Paine calls the seeming edge for teams who get the ball first "small but meaningful." When I chatted with him, he noted that it's slightly smaller than the home field advantage (i.e. the home team wins about 14 percentage points more often in the regular season) "but still matters if it's persistent."  
        Put another way, a great team is still likely to beat a bad team in overtime. But when the teams are fairly evenly matched, getting the ball first probably matters. 
        The playoffs is such a time when the teams are usually fairly evenly matched. Although the sample size is just 11 games, the team that has gotten the ball first in overtime since 2011 has won 10 times -- a small sample size but a pretty big statistical departure.
          Just ask any Atlanta Falcons fan about Super Bowl LI in 2017, when the New England Patriots won in overtime without the Falcons offense ever taking the field. The Patriots did the same thing to the Chiefs two years later in the AFC Championship game. Now, the Chiefs have done it to the Bills.
          There's a reason many Falcons fans cried foul after that Super Bowl. Today, many Bills fans know the pain.