QB Fragility Update

Submitted by MCalibur on April 24th, 2010 at 4:57 PM

My first diary ever was a look at the hypothesis that option QBs get hurt with a higher frequency due to the extra hits the are exposed to. I followed that one up with an expanded data set to include 5 seasons instead of 1. This update adds 2009 to the set and gives the helihat a spin that I had not gone through the trouble of in the previous diaries.

For the forcier-like detail on what was done, please refer to those diaries and discussions. But here’s a high level summary:

  • The scope was all FBS schools and all QBs with significant playing time. Significant playing time is defined as players who average more than 17 plays (passes + runs) per game they played in. This level is based on the median of the data (50-50 split on either side of the line).
  • QBs were binned into 4 groups according to their run-to-pass ratio.
  • Injuries and games lost (quarter game resolution) were tracked and statistic-ated.

Here’s the data. Sorry for the table not being copy&paste-able, Windows Live Writer was not cooperating with me.


Last season was a bad year for non-zero threat level QBs with levels 1-3 coming in above 30%. It’s important to note here that sample size is a factor in this. For example, each level 3 QB accounts for about 5% of that population so one injury sways the percentage by quite a bit. This is a big reason why there is so much variation in the injury rates for levels 1-3 from year to year. The aggregate totals are much more reliable because, at this point, each category has plenty of observations with which to make conclusions.Fragility plot

The graph above shows the overall range (black line),  average (red circles), and the standard error of the average (red hashes) for each category. At first blush it looks like there’s a difference in the injury rates of level 1, 2, and 0/3 but the fact of the matter is that there is insufficient evidence to support this. I actually ran hypothesis tests this time and that was the outcome (failure to reject the null hypothesis that A=B=C=D). Note that this does not mean that no difference exists, simply that there is no reason to conclude that a difference does exist. The differences observed are statistically insignificant.

People who believe that option QBs get injured more often do so because that’s what they want to believe.


Blue in Seattle

April 24th, 2010 at 8:56 PM ^

Both your links lead to the first article?

This is great stuff. For me in a subjective non-statistical estimation, injuries on QB correspond more to the quality of offensive line and frequency of desperation plays.

I don't remember Henne ever being injured his freshman year, but his senior year seems to standout as one of constant injury.


April 24th, 2010 at 11:23 PM ^

tater was suppossedly injured from game 5 on last year but missed no games.
it seems you may be able to conclude that no statistically significant differences in number of missed games were seen between groups.
it is unclear from this post but can there be injuries which allow the qb to play but at a much less effective level?


April 25th, 2010 at 12:59 AM ^

The conclusions still stand, though. It's all in our head.

The fact is that football is a violent sport and guys at every position play with "minor" injuries. Note the pun (which was not intended). There are many other examples besides Forcier. Tebow is another one the got injured (concussion) but didn't miss a game; Florida had a BYE the following week. Jimmy Clausen had turf toe for a big portion of the season which probably led to more sacks or throw-aways than may have otherwise happened.

I've accounted for this reality as much as I can by counting missed games in quarter game increments rounded down. That is mentioned in the second article. Basically, if you get a concussion (or whatever) in the second quarter and miss the rest of that game then come back in the next game, I log 0.5 games missed and the QB shows up in the ranks of the casualties. If you get knocked out in the fourth quarter and come back the next game, you don't get counted because you didn't miss any whole quarters of football.

However, these aren't the injuries that people are worried about (the minor ones). The claim is that an option QB is an unnecessary risk because they are more apt to get injured. This study proves finds that there is no evidence to support that claim. If you're hurt but able to play and actually do then, you're not injured in the context of football; you're a tough guy.

Machoism aside, where should the line be drawn? Do bruised ribs count? Should we measure how many rolls of tape a guy puts on his ankles to make sure he didn't tweak one last time? Hell, Tony Pike had a soft cast on his hand in a few games. I think the only sensible line that can be drawn is missing a whole quarter or more of football. That's the best that can be done with out combing through the medical records of all 120 or whatever FBS programs. Pretty hardcore but, 'tis what it is.

Thanks for engaging your intelligence. +1.

[Should Sam Bradford count twice? In my study the answer is no; each individual QB is only counted once per season. That is VERY rare situation (he's the only one I can think of), but technically he got injured twice last year.]


April 25th, 2010 at 4:22 PM ^

My intuition says that pocket passers are at least as susceptible to major injury because they tend to be hit when least prepared for it. The Level 3s are getting tackled more but expect it and absorb the hit more like a running back.

All types of quarterbacks can be injured. From a team perspective the key is to have capable backups similar in style to the starter. Either Oregon with Dennis Dixon out or WVU with Pat White out is a severely depleted team. With Forcier, Robinson and Gardner all in the program Michigan will be much better equipped to ride out an injury.


April 26th, 2010 at 4:49 PM ^

I think they are all equally at risk of being injured no matter the scheme. Their is always a risk of getting hit while your planting to throw or while your on the run.


April 27th, 2010 at 6:37 AM ^

Interesting stuff - I've also wondered if there is any correlation between the weight of the QB and the probability for injury. I started thinking about how height and weight are interrelated, but then I reached the conclusion that with rare exception most QB's need to be 6 feet or taller in order to be able to see over the "trees", compared to RB's who can be shorter and heavier and it doesn't impact their ability to run.

In real terms, I was thinking about Denard and Tate compared, say, to a Juice Williams, or eventually, after Barwisizing, DG.


August 14th, 2013 at 10:51 AM ^

I think that there is a good deal of data to be mined here, and that there are a number of interesting questions to answer.
1. Is there an effect of what class the QB is on the probability to get injured?
2. Can we come up with a better stand-in for threat level? I have never liked that choice for a few reasons.
a. It is purely subjective.
b. It isn't scalable. (How can you tell the threat level of Joe Blow, the QB for Nobody Cares U?)
My better idea would be to replace by offensive system. WCO, pro, air raid, option. And to include individual abilities by looking at (sack corrected) YPC or other rushing stats.
3. Should other positions be concerned based on the offensive system they play in? RBs, TEs, WRs... Getting good data on the RBs might be easier, and exploring those relationships might be instructive for learning about QBs.

I would look at some of these, but I'm too lazy to go get the data. Sometimes I wish there was a good place to get data easily that I can import into R...