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Do Justin Fields’ Rookie Fumbles Portend a Fumbler? Data Says It’s Unlikely.

| May 17th, 2022


Despite only starting 10 of 17 games last year, Justin Fields fumbled the ball 12 times, which was the 4th highest mark in the NFL. That’s a real problem. Since fumble recovery is random, meaning you will lose roughly half of your fumbles, that’s an additional turnover around once every two games. Given the strong relationship between turnovers and game outcome, this is a recipe for losing a whole lot of games.

But is this a problem that is likely to continue for Fields? Let’s see what history might be able to tell us.

Fumbling Rookies.

It is surprisingly common for rookie QBs to fumble the ball. A lot. Since 2001, there have been 24 instances of a rookie QB fumbling the ball ten or more times. Looking at the rookies who have played the most, there are 61 rookie QBs in that time span with at least 250 pass attempts, and 22 of them (more than 1/3) had at least ten fumbles.

So, in that regard, Fields is in good company. While many of the QBs on that list went on to bust status, there were plenty of successful QBs as well, including Lamar Jackson, Andrew Luck, Derek Carr, Alex Smith, and Carson Wentz as long-time starters.

This led to a logical follow-up question: do QBs who fumble a bunch as rookies improve after that? In order to explore this, I tracked fumble rate through two methods:

  • Plays per fumble, which includes all pass attempts, sacks, and rushes. This is a measure of how often a QB fumbles compared to how often the ball is in his hands.
  • Hits per fumble, which includes all sacks and rushes as plays in which the QB got hit. This is a measure of how often a QB fumbles when exposed to contact with the ball in his hands.

I should note that this list only includes QBs who had 1000+ career pass attempts total, such that there was a large enough post-rookie sample size to gather meaningful data. This gave a sample size of 17, which includes over 8,000 rookie plays and 40,000 non-rookie plays.

The table below shows how QB fumbles compared for these 17 players as rookies compared to the rest of their career. I provided the high, average, and low marks for a good idea of the range of outcomes.

A few thoughts:

  • You can see the dramatic improvements made across the board by both plays/fumble and hits/fumble. In fact, 16 of the 17 QBs studied improved in both categories from their rookie season to the rest of their career, indicating that this is a nearly universal trend we should expect to see in Fields going forward.
  • In his rookie season, Fields came in at 32 plays/fumble and 9 hits/fumble. His combination of holding the ball for a long time and taking off to run fairly frequently exposed him to more hits than most, which accounts for the discrepancy in where those sit relative to the sample above.
  • When looking at year-over-year correlation, hits/fumble had a much stronger relationship than plays/fumble (r² of 0.44 vs. 0.10, respectively). That bodes well for Fields, who did better in hits/fumble, but he could also improve on his fumbling by taking fewer hits. His legs are a real weapon, so I don’t think he should try to avoid running, but he can certainly do a better job of getting the ball out before taking a sack.

All QBs.

Next, I want to give a little more context to the discussion about fumble improvement. Those who fumbled a bunch as rookies fumble less later in their career, but are they still fumble-happy compared to other NFL QBs?

In order to explore this, I looked at all NFL QBs with at least 1000 pass attempts since 2012 and compared their fumble rates to the fumble-happy rookies, both for their rookie season and then the rest of their careers. I narrowed the time range here because I want to see more relevant recent examples, and it’s also quite a large sample size for expanding to all QBs (55 total QBs, 8 of whom had 10+ fumbles as rookies). The results can be seen in the table below.

A few thoughts:

  • Both groups of QBs see their fumble rates improve appreciably after their rookie season, but those in the 10+ fumble as rookies sample see much more dramatic improvement. This means that the gap between the two samples is closed significantly in their post-rookie seasons, though those who fumbled more as rookies still tend to fumble a little more frequently than their peers on a per-play sample.
  • Here we see the fumble rates on a per-hit basis are functionally identical after the rookie season, meaning non-rookie QBs who fumble more do so primarily because they get hit more. Fields’ playing style means he will likely always fall into this category.

Lessons Learned.

Rookie QBs fumble quite a lot in the NFL, which makes sense given that they are getting used to the speed of NFL defenses and have to adjust their play clocks accordingly. Virtually all QBs end up fumbling less frequently as they gain more experience, so we can expect Fields to do the same. Fumbles will likely always be an issue for him, but if he shows typical post-rookie improvement, they won’t be a deal-breaker.

Fields fumbled the ball 12 times as a rookie, which closely matches what Lamar Jackson did in his rookie year. Jackson has seen that average drop to around 7 fumbles/season in his post-rookie career so far. There are a whole host of other NFL QBs in that same range, as Russell Wilson, Kirk Cousins, Derek Carr, Ryan Tannehill, Dak Prescott, Josh Allen, Deshaun Watson, and Kyler Murray have all averaged between 8 and 10 fumbles/year in their careers. It seems reasonable to think Fields will likely end up in a similar range, which is perfectly acceptable.

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