Every year, especially at draft time and heading into the season, fans are treated to a lot of potentially unfamiliar vocabulary. Three-technique or five-technique. This or that cornerback can or cannot flip his hips quickly. Statisticians have more categories than ever, even for things that are purely imaginary, such as Wins Against Replacement.
This article will examine some quarterback terms and how they relate to head coach Kyle Shanahan and his starting quarterback.
Completed Air Yards per Pass Completion (CAY/Comp)
Receivers are often judged on the yards they get after the catch, and some judge quarterbacks according to how much yardage the receiver was responsible for. CAY/Comp measures the yards the ball traveled past the line of scrimmage before it was caught and therefore reflects the quarterback's portion.
It is not surprising, then, that Los Angeles Rams quarterback Matthew Stafford was third in the league last year in that category. He has a big arm and good receivers. It would also point to an offensive system that likes the deep ball. The 49ers quarterbacks have historically been accused of short passes with a lot of run-after-catch yards.
However, even playing hurt, Niners quarterback Brock Purdy was eighth in the league last year in CAY/Comp, well ahead of the Bears' Caleb Williams and Green Bay's Jordan Love, for instance. In 2024, Purdy was third in the league. In 2023, he was second. Brock has been accused of being a dink-and-dunk thrower, wholly dependent on his receivers to do the damage. That is clearly not true.
One would expect those who have high CAY/Comp numbers to have lower completion percentages. That is usually fairly true. In 2023, for instance, Stafford was fifth in CAY/Comp and 26th in completion percentage. CJ Stroud, who led the league in CAY/Comp that year, was 23rd.
In 2023, Purdy, who was second in CAY/Comp, was ... 4th in completion percentage. Last year, he was eighth in CAY/Comp and second in completion percentage. He is an outlier when it comes to longer throws and high completion percentage. Brock led the league last year in on-target percentage and was fourth lowest in bad throw percentage. This tells us how Shanahan prioritizes plays he likes to call and what he needs in a quarterback.
Intended Air Yards (IAY)
While a CAY/Comp number reflects completed passes, the IAY measures the air yardage of all throws. To an extent, it therefore gives a clue to the coach's offensive philosophy. How many deep passes are called?
It is not surprising that some of the big-armed quarterbacks, Stafford and Jacksonville's Trevor Lawrence, led the league last year. Williams is known for his arm, and he was third, and his head coach, Ben Johnson, who turned Detroit into a scoring juggernaut when he was the offensive coordinator there, has no problem calling for the deep ball.
What might be surprising to some is that Shanahan called a lot of longer throws. Purdy and back-up quarterback Mac Jones combined for what would have been eighth in the league, well ahead of the Chiefs, Packers, and Seahawks, who are all known for quarterbacks with big arms.
QBR
There are two quarterback rating scales: the passer rating and the QBR. The QBR is more comprehensive, taking into account not only yardage, touchdowns, and interceptions, but also penalties, rushing, and even the context of a play.
It is no surprise, then, to see the star quarterbacks atop the leaderboard in that category. It takes into account anything that helps (or hurts) the team's chances of winning, and the quarterback is the most important position on the field. So it should come as no surprise to the haters that...
Brock Purdy was second in the league in QBR last year, seventh in 2024, and he led the league in 2023.
He has a good surrounding cast, but he is helping them play better, too. Shanahan and general manager John Lynch have focused on acquiring good position players. Still, they have done so with an eye not only to how certain kinds of players can help Purdy but also to what kinds of players will benefit most from Purdy. Chemistry is not one-directional.
Tight-window throws
This is one of the most interesting stats to me. NextGen Stats defines a tight-window throw as one in which the receiver has less than one yard of separation. In some ways, this is the best measurement of a quarterback's accuracy. In 2023, Purdy was fourth in the league. In 2025, he was third, 0.2 behind teammate Mac Jones.
We know Shanahan (as did Bill Walsh before him) prizes accuracy above all else, and Purdy's excellent completion percentage and tight-window throw success show why Shanahan and general manager John Lynch were more than happy to sign him to a big contract.
Batted passes
This statistic is fairly self-explanatory, but I include it here because of the obsession at the NFL Combine over a quarterback's height. The powers-that-be wring their hands over how a shorter quarterback might get passes batted down at the line of scrimmage. While it is true that some diminutive quarterbacks get balls knocked down more frequently—Tampa Bay's Baker Mayfield, Arizona's Kyler Murray—it does not explain why so many taller quarterbacks do, also. For instance, the 6'6" Lawrence led the league in batted passes last year with 20. That's over one per game for someone taller than most of the offensive and defensive linemen.
And other quarterbacks who are a little shorter but faced no scrutiny on that front—Minnesota's 6'3" JJ McCarthy, for instance, who had 16 swatted away in only ten games, or Detroit's 6'4" Jared Goff—are frequently at the top of the list. Brock Purdy is 6'1", and he has been consistently behind numerous tall quarterbacks.
Last season, in his nine games, Purdy had only four passes batted down. Prorated over a full season, that would have put him toward the bottom of the league. His 6'3" teammate, Mac Jones, had more.
There are far more categories I could go over (and you can find a comprehensive table here), but I wanted to focus on the ones most relevant to the Faithful.
Since 2019, excluding two seasons when injuries ravaged the club, San Francisco is 60-24, and owns a winning percentage of .714. They have gone to two Super Bowls, four conference championships, and, last year, in a season when injuries again decimated them, made the playoffs and won a game.
In other words, they've been one of the most successful franchises in the league.
What the stats show is Kyle Shanahan's philosophy and how he has married it to his quarterback's skills. And if history can predict success or failure, if the team is healthy, that success should continue.
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