By Brian Burke
The interactive visualization below chart's each player's career. It's a special version of the QB viz I update weekly throughout the season. In this edition, I've selected only Manning and Brady for comparison, plus I've included postseason data.
The viz offers two unique and innovative ways of looking at each player, unashamedly stolen from the best baseball analytics site on the Web, Fangraphs. First, there is a plot of career cumulative Win Probability Added (WPA) from each QB's first year through his most recent year. It's an interesting way to compare the career trajectories of top passers because it's a cumulative chart.
Second, there is an "Nth best season" Expected Points Added (EPA) chart, which takes some thinking to understand because it's not plotted in chronological order. It plots each QB's season in order from his best EPA season through worst EPA season. It's not cumulative and because it appears to trend downward does not mean the QBs are declining. I like it because re-ordering each season makes the separation between each player's performance clear to see.
There are a couple caveats. The data only goes back to 1999, so it misses Manning's rookie season. Remember that Brady only played mop-up duty in 2000 and only played a few snaps before being injured in 2008. Manning missed all of 2011, so unlike Brady's 2008 it doesn't show up as a 'season' for Manning at all.
Just from these numbers, and assuming all else equal, you'd say that Manning > Brady. But all else is not equal. Aside of offensive teammates, defenses play a role. Because Brady played on teams with better defenses than Manning, his EPA production did not translate into as much WPA as Manning's did. A touchdown pass to put your team up 35-31 would generate much more WPA as a touchdown pass that would make the score 35-3. Still, Manning appears to out do Brady in EPA as well as WPA.
The one thing Brady had over Manning was that his peak was higher. Specifically, his 2007 season was the best on record for any QB. But at age 37, Manning has now nearly matched Brady's peak with two games potentially left to play. In fact, their two top seasons are nearly identical in terms of EPA.
Remember the numbers are only the start of the conversation, but if we're going to talk numbers, we might as well use good ones.