In 2019 the National Football League (NFL) released an article – “Top 25 quarterbacks of all time: Patriots’ Tom Brady leads list.” The two quarterbacks who trailed for 2nd and 3rd place were Joe Montana and Peyton Manning, respectively.

Now it has been 5 years, and Kansas City Chiefs quarterback Patrick Mahomes has burst onto the scene, winning an astounding 3 Super Bowls. Talk has entered the football world about whether Mahomes should be considered in the debate as one of the GOATs.

Should Mahomes be considered in this conversation? Could one even argue that he is the GOAT?

My initial thought in conducting this project was that I could not trust the opinion of a single NFL journalist, Elliot Harrison, on a matter so seemingly controversial. After all, it was not as if Harrison conducted a rigorous statistical analysis to prove Brady the best, and even if he had, I would still be skeptical. This is sports after all, and there are likely thousands of factors at play here.

So I turned to public opinion. In a poll conducted last year by third party-data company Statista, I found Harrison’s opinions to be respectable. Forty three percent of 2,203 responding fans identified Brady as the GOAT, with 11% voting Montana, 7% Manning and 4% Mahomes. Note that this poll was conducted last year, before Mahomes went on to win Super Bowl LVIII and tie Montana’s MVPs in the championship game with his 3rd.

With the small sample size of respondents, and without another poll conducted after this year’s Super Bowl, I figured I would need to get into player statistics to formulate an opinion of my own. But first I wanted to further familiarize myself with each players’ career.

Here (https://willhamlin.shinyapps.io/QuarterbackTimelines/) is a link to a Shiny app that includes a timeline with major moments in each players’ career. It can be sorted by quarterback, and the first thing that stands out amongst the comparisons is Mahomes’ rapid progression in the league. In only his second year in the NFL he won the NFL MVP Award, an award that took Manning 5 years to win, Brady 6, and Montana 10. Another interesting takeaway is that Manning, Brady and Montana all won NFL Comeback Player of the Year at some point and each played for more than one team. Injury and a different team are two things Mahomes hasn’t experienced yet, so while his career may have a quicker start, it really lacks the responsiveness to adversity that we see in the other 3 greats. His career is just too short so far to fairly compare the 4 quarterbacks in such a manner.

With this, it will be important to turn the more statistics-based approach I originally had in mind.

Here (https://willhamlin.shinyapps.io/NFLQuarterbackStatsComparison/) is a link to another Shiny app that allows us to compare 2 quarterbacks at a time in terms of touchdowns, interceptions or yards. There appears to be a clear disparity among quarterbacks who have played more seasons (Brady) and those who haven’t (Mahomes). Brady wins in all 3 categories while Mahomes loses. This illustrates the difference in sheer volume between the 4 quarterbacks and provides information that leads us to another comparison strategy: average statistics.

Below is an animation of each quarterbacks’ passer rating for their first 7 seasons in the league. Passer rating is a metric measured from 0 to 158.3 that takes into account a player’s passing attempts, completions, yards, touchdowns and interceptions. In the graphic, it is immediately clear that Mahomes is on top. He wins in 5 out of the 7 seasons, and his 2nd season (MVP) isn’t even close. However, in season 7 we see Manning dominate with a passer rating above 120 which showcases the need to look further at career statistics, albeit normalized ones.

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In a Bleacher Report article titled “Which Metric Matters Most When Evaluating NFL Quarterbacks?” by Brad Gagnon, the three most telling (aside from passer rating) are stated to be yards/attempt, completion percentage and touchdown % over interception %. Below is a career comparison of these metrics among our quarterbacks. We can see Mahomes wins in each category, especially dominating in the most telling category, TD%/Int%, as this metric directly impacts game score. He has a TD%/Int% of 3.39, which beats out the next closest at 3.00 (Brady) and blows Montana’s 1.96 out of the water.

Now it is clear Mahmoes is the best of the 4 at passing. However, we must take into account that Brady, Montana and Manning played many more seasons than Mahomes has. They played through multiple eras of football and encountered many more defensive schemes. The game is likely not the same today as it has been in the past, so we can simply look at each quarterback’s ability to win. In the scatterplot below, the impact of # of games played on # of wins and losses is clear. Each quarterback has more wins and losses than the last based on playing more seasons. However, upon toggling over the dots, the reveal of winning percentages allows us to see Mahomes again takes the cake. His career winning percentage of 77.08% beats out the next closest contestant, Brady, who has a career winning percentage of 75.38%.

Winning percentage is great, but in the debate for the GOAT in any sport, many would say championships are the most important deciding factor. So, even with Mahomes’ short 7 seasons compared to Brady’s 23, how does he stack up? Well, from the below graph, it is evident his 3 rings are far behind Brady’s 7. However, Mahomes’ ratio of winning to non-winning seasons is by far the best. He has won Super Bowls in 3 out of his 7 seasons in the NFL. That is almost 50%! Additionally, with the hover text one can see Mahomes has won the SB MVP in each of his wins, beating out Montana’s renowned clutch ability, who has 3 MVPs in 4 championships. If Mahomes continues performing at this level for even another couple years, few would likely argue against his GOAT status.

So far it appears Mahomes wins in every category. The only thing holding him back from GOAT status is sheer volume of wins and Super Bowls due to his short tenure in the league. While there is a lot to be said for dominating over a 23 year career, I believe there is still a place for normalized statistics in making an argument for a player who has not played as long. One way to do so is to take into account how a quarterback stacks up against others of his era. This can be done using QB Elo Value, a metric created by 538 (part of ABC News) that predicts how much impact a player has on a game’s outcome. The Elo value takes into account even more statistics than passer rating – things like opposing defensive strength.

However, passing has become more prominent in today’s game than it ever has been. Therefore, it is necessary to normalize Elo and use era-adjusted Elo, which is what I’ll be using.

Below is a graph showcasing each quarterback’s average Elo per game throughout their career. It should come as no surprise at this point that Mahomes wins again! His Elo/game is a remarkable 112.4 while Brady’s sits quite low at 72.8. While this metric can be confusing, using hover text reveals the percentage of games where that quarterback had the best Elo in the NFL. Brady spending 14% of his games as the best QB does not seem shabby, but Mahomes’ 47% is almost otherworldly.

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With insight into so many fields where Mahomes beats out the supposed “top 3 NFL QBs of all time,” is it time to at least consider him for the top spot? I believe it is.