According to reports, Kyle Shanahan says he expects Brock Purdy back for training camp. This is welcoming news for a San Francisco 49ers organization that was previously operating under relative uncertainty as to who their opening-day quarterback would be after Purdy suffered an elbow injury in the NFC Championship Game.
With Purdy set to be ready for training camp, the obvious question is, does he deserve to be QB1 on the depth chart come opening day? Many believe Purdy stepped into an already humming offensive powerhouse with a game plan that took a lot of pressure off of him. However, compared to the other two quarterbacks who played in San Francisco, behavior science tells us Purdy was more than just a placeholder.
Brock Purdy Is the 49ers’ Best of the Rest
Trey Lance is the first player who comes to mind as to who else can claim to be heir to the 49ers’ throne. It wasn’t long ago San Francisco gave up a haul to move up and acquire him in the draft. Why hasn’t he been able to cement himself as the guy?
Meanwhile, Jimmy Garoppolo is now in Las Vegas. While he stabilized the 49ers’ offense last season when needing to step in for Lance, there’s a reason Garoppolo wasn’t brought back. His time had run out to establish himself as more than what he had been.
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This year, Sam Darnold will take his place as the veteran presence. The operating theory was that Darnold would be the opening-day starter until Purdy was healthy. But would he have been able to hold the job? Unlikely.
The Case for Brock Purdy
Yes, the 49ers won games with Jimmy G stepping in. In nine complete games, the Niners were 6-3, and he was San Francisco’s perfect game manager. You could argue that Purdy stepped into the same great situation Jimmy G did — because he did.
But he did it better.
In those completed games, Garoppolo helped the 49ers to a .67 scoring behavior rate. This means they were scoring about two-thirds of a point every minute of possession time. Purdy, however, came in and elevated that number by 47%. That is the third-largest increase between two players at the QB position in all of 2022, and the only one involving a veteran giving way to a rookie.
Purdy came in and led the 49ers to what would have been a top-three scoring behavior team in the entire NFL. With him under center, San Francisco averaged .99 points per minute of possession time. Only two teams finished above one full point on average.
Purdy started seven games, and San Francisco scored above one point per minute of possession time on five occasions. In fact, if you remove the two outliers, the 49ers would have had the best five-game stretch of scoring behavior rate of any team in the NFL last year.
For further perspective, Garoppolo started 10 games, and the 49ers scored above one full point per minute on average just twice. Lance, meanwhile, has never started a game where the 49ers scored above .8 points per minute of possession time, and twice started games where they scored below .4.
But What About Christian McCaffrey’s Presence?
This was a common talking point in 2022. Christian McCaffrey came over, and that seemed to be the real spark for the 49ers, and Purdy was just along for the ride. However, behavior science tells us a different story.
McCaffrey was the full-time starter for six full games before Purdy took over. He had more of an effect on the Garoppolo-led 49ers than he did on the Purdy version. Without McCaffrey, Garoppolo led the 49ers to a .63 scoring behavior rate. After acquiring McCaffrey, that number jumped by just 13% during those six games, with San Francisco averaging .71 points per minute of possession time.
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It wasn’t until Purdy became the starter that the team took a massive jump. If you parse out the difference between the six games with McCaffrey as the starter, where Jimmy G was the starter, compared to the environmental change of having Purdy in, the numbers are much larger.
The jump from .71 points per minute of possession time to .99 during the Purdy tenure is 40%, compared to a 13% increase with Garoppolo.
McCaffery mattered, Purdy mattered more.
The Case Against the Rest
It’s one thing to advocate for someone. Purdy’s numbers are pretty clear and with enough evidence to make the case open and shut. But that’s only true because when held up against the other cases for the other players, it puts it all into focus. The reality is that no other player has done for the 49ers what Purdy has.
For some, it’s even more glaring than what was laid out in the case for Purdy, and for others, they’re likely going to simply be a victim of circumstance. Either way, Purdy is the best of the rest.
The Case Against Trey Lance
Lance was always going to be a project, even when the 49ers selected him. Simply put, he’s barely played any meaningful football since high school. He barely played one full season across three years at North Dakota State. Then, in the NFL, he could barely stay healthy.
So how do you assess a player who has played in 24 games since 2020? While you could argue that San Francisco needed to give him time to develop, the other quarterbacks have outplayed him at every turn.
Lance has started and completed three full games in his two professional seasons. The 49ers have averaged 14 points in those games, scoring just 10 in two of them. Furthermore, if we take those three games and hold them up against Garoppolo’s and Purdy’s 2022 starts, they fall well below the mark.
In Lance’s three games, the 49ers had a scoring behavior rate of just .41 points per minute of possession time, and that number was decelerating week over week by 23%. If that number held true throughout the 2022 season, San Francisco would have finished with the worst scoring behavior rate in all of football.
Compared to Jimmy G, who helped the 49ers to a .67 scoring behavior rate across 10 starts, Lance was ~80% worse. Compared to Purdy, who helped the team to a .99 scoring behavior rate, it’s much, much worse.
The Case Against Sam Darnold
When Darnold was named the Carolina Panthers starter late in 2022, there’s no doubt his presence stabilized a dreadful offense. With him as the starter, the Panthers averaged .82 points per minute of possession time — a 58% increase from PJ Walker’s six starts.
Yet, it would still be well below what Purdy accomplished in San Francisco. Working against Darnold is his journeyman status. He’s had years to be the guy and couldn’t get it done in New York or in his two years in Carolina. If Shanahan is picking between a journeyman or his second-year player who’s proven success in your environment, the coach is going to pick the homegrown young guy every time.