Colin Kaepernick pass charting project begins

Seven hundred seventy. That is the number of passes launched from the right arm of San Francisco 49ers quarterback Colin Kaepernick in his 29 career games as a starter. And over the course of the last few weeks I went back and watched every single one of them.

As we wind down the final days until the start of the regular season I'm going to be attempting to address some of the most significant questions and concerns people have had about Kaepernick to this point in his career. I'll also be digging deeper into San Francisco's passing offense as a whole and looking at some of the most frequently used passing concepts that the 49ers have called in Kaepernick's time as the starter.

As for this first post, consider it a data dump of some of the information that I accumulated during this process. Some of it may be things you already knew, some tidbits are more interesting than others and some parts of the data is certainly more meaningful than other parts. But I learned quite a bit while starting to organize all the information that I collected and the hope is that you will as well.

Before we get to the good stuff, a few things to keep in mind as you're reading through the numbers.

First, plays that began as passing plays but that ended up with Kaepernick scrambling are not included in the dataset. Because scrambles are ultimately run plays, they don't show up when searching for Kaepernick's passing plays in Pro Football Reference's Play Index, which is what I used to gather all of the standard play-by-play information as well as get the list of plays that I needed to watch. For the most part, this won't have a significant effect on most of the information I'm going to cover as the focus was going to be primarily on the plays Kaepernick put the ball in the air anyway. We do lose out on some of the personnel and formational information, but it's a minimal loss in my mind.

Passing plays in which Kaepernick threw the ball away were removed before calculating most of the numbers that you'll find below. For the purposes of things like completion percentage and yards per attempt, I'm more interested in finding out how Kaepernick is performing on plays were there was actually an intended receiver.

Finally, there's a good amount of subjectivity involved with several aspects of the information I collected. From the intended receiver's location on the field to the accuracy of the pass to the design of the play, there were definitely judgement calls that had to be made. While you can trust that every effort was made to remain as consistent as possible when tracking all this stuff, there are definitely going to be imperfections. But given we're working with a pretty solid sample of plays here, it shouldn't significantly skew the types of things that I'm going to be covering.

With all that out of the way, let's get to it.

Yards per attempt

• Kaepernick's yards per attempt steadily increases the farther downfield he throws the ball, going from 5.63 yards per attempt on 56 passes thrown behind the line of scrimmage up to 13.32 yards per attempt on 106 passes that traveled 20 or more yards in the air. Nothing surprising here, this is exactly what you would expect.
• When throwing vertical routes to the seams—roughly the area between the numbers and the hashmarks—Kaepernick has had a ton of success. On 35 passes that traveled 10 or more yards in the air to the left seam, Kaepernick averaged 15.03 yards per attempt. To the right seam, he averaged 14.54 yards per attempt on 44 passes.
• Granted it's a small sample size, but the 49ers haven't had a lot of success throwing WR screens. Throwing more screens—both to wide receivers and running backs—is a common request among fans but there's just not a ton of evidence that points to screens being something that San Francisco does well. On 30 passes behind the line of scrimmage to the left or right sideline—nearly all of which were screens—Kaepernick averages just 5.43 yards per attempt.
• An area that the 49ers may want to try and attack more frequently is to the intermediate middle of the field. Kaepernick has thrown just 18 passes to this area over the last two seasons, but he averages 10.72 yards per attempt when he does.

Completion percentage

• When looking at Kaepernick's completion percentage by target location, we again see an expected trend with higher percentages coming on throws closer to the line of scrimmage and a steady decline the farther downfield his targets go.
• Just as with yards per attempt, we see that Kaepernick has had a lot of success throwing to the seams. Using the same parameters as above, Kaepernick completed 60 percent (21-of-35) of his passes to the left seam and 66 percent (29-of-44) of his passes to the right seam.
• Kaepernick has been terrible when throwing to the deep middle of the field, completing just 25 percent (4-of-16) of his passes to this area of the field. In 2013 he completed just one of his 10 attempts to the deep middle. His saving grace when throwing to this area has been that when he misses, he at least misses long where he's less likely to be intercepted. Of the 11 passes that I marked as being inaccurate, nine of them were overthrown.
• When throwing short—less then 10 yards but beyond the line of scrimmage—Kaepernick has spread his throws very evenly across the field with between 65 and 82 passes attempted in each of the five areas that I split the field into. And as you can see from the image above, his completion percentage has also been very consistent to each of those areas.
• Once you get beyond 10 yards from the line of scrimmage, Kaepernick has a clear preference for throwing to the sidelines. Kaepernick has attempted 91 passes to the left sideline and 101 passes to the right sideline when the ball travels at least 10 yards downfield. The next closest area is the right seam, where he's attempted 44 passes. This is at least partially due to the type of route concepts the 49ers prefer to run when attacking down the field, something I'll be covering in more detail in a later article.

Accuracy

• On each throw I marked whether the pass was accurate, overthrown, underthrown, thrown away or one of a couple other rarely used classifications. This obviously gets pretty subjective, but I tried to stick with simple definitions for each. Overthrown covers any pass that was either too high or too far in front of the intended target. Underthrown is for passes that were either too low or too far behind the receiver. Thrown away was for passes that obviously had no intended target and were thrown out of bounds.
• Accuracy percentage is similar to completion percentage but considers whether I marked the pass as "accurate" rather than if it was simply complete or not. Put another way, a pass did NOT have to be completed to be marked as accurate. This is primarily to account for dropped passes, but there were a few other things I was looking for as well. I considered the type of throw being made (throwing a back shoulder fade is different than throwing a crossing route), the placement of nearby defenders (is the ball thrown away from the defender in a spot that gives the receiver the best chance to make the catch) and when warranted, whether the ball placement allowed the receiver to easily run after the catch.
• As mentioned previously, this chart does not included passes that were marked as thrown away. The idea here is to get an idea whether passes are put were they need to be when the ball is actually thrown to a receiver.
• In the aggregate, Kaepernick's accuracy percentage (64.8%) comes out nearly identical to his completion percentage (64.0%) and most of the significant differences between the two in specific areas of the field can be explained away by small sample sizes. This makes me think accuracy percentage probably isn't any more useful of a metric than completion percentage, but I decided to go ahead and share the data anyway.
• When Kaepernick did miss, he had a very slight tendency to underthrow the ball. On targeted passes, I marked the pass as underthrown on 17.2 percent of passes and overthrown on 15.9 percent of passes.
• Kaepernick was most accurate on passes to the middle of the field with his accuracy percentage declining as you moved towards the sideline. This makes sense as throws to the sideline have to travel farther in the air than passes to the middle of the field.

Personnel and formations

• San Francisco used either the Pistol or Shotgun on 61 percent of pass plays.
• When in the Pistol/Shotgun, the 49ers used play action 17.1 percent of the time. Their play action percentage went up to 48.3 when Kaepernick started under center.
• The 49ers put four wide receivers on the field at the same time on just five total pass plays, less than one percent of the time. Along those same lines, San Francisco had just 11 pass plays (1.3%) in which there were no running backs on the field.
• Given the previous note, the 49ers lined up with an empty backfield more often than you would expect, doing so on 51 pass plays (6.1%). They would frequently line up a running back to the outside in order to try and get one of their primary pass targets matched up with either a linebacker or safety in the slot.
• Not going to get into a ton more specifics in this area for right now, but there will definitely be more in coming articles.