We no longer have to reference completion percentage for quarterbacks when statistics like on-target percentage exist. But it seems like we’re introduced to a new metric every year.
Pro Football Network is the latest site to produce a metric we’ll discuss today. They call it “QB+.” Here’s the definition:
The QB+ metric is a formula that assigns a letter grade to each quarterback’s performance. The metric takes into account stats like success rate, third-down conversion rate, and pocket production. It also considers “clutch” performance, which is quantified using timeliness-based stats.
Once I read success rate, my interest was piqued. It’s a number that considers what happens over the course of the 60-70 plays in a game instead of being skewed by a pair of big plays, which is one of the biggest issues with “expected points added.”
For example, expected points added favors quarterbacks like Jordan Love and Sam Darnold, while success rate appreciates the Jared Goff’s and Matthew Stafford’s of the world.
Back to “QB+.” When looking at a new metric, you might want to look at who is at the top and who is at the bottom. For QB+, Lamar Jackson, Goff, Josh Allen, Jalen Hurts, and Joe Burrow had the five-highest scores in 2024. The worst scores this season were Deshaun Watson, Spencer Rattler, Anthony Richardson, Cooper Rush, Gardner Minshew, and Will Levis. We can all agree on which group of quarterbacks you want to be associated with.
San Francisco 49ers quarterback Brock Purdy ranked sixth, behind Baker Mayfield, in QB+:
Brock Purdy, 49ers
Brock Purdy, San Francisco 49ers
Regular Season QB+: 87.6 (B+; 7th)
We may not hear much about Brock Purdy over the next month or so with the San Francisco 49ers not making the postseason. However, this is likely to be an offseason that prominently features him as he becomes eligible for an extension for the first time in his career.
2022’s Mr. Irrelevant has done everything he can to prove he deserves a big-time deal. Amazingly, a B+ with an 88 score is actually Purdy’s worst QB+ of his career. He did not throw enough passes to qualify as a rookie but was on pace for a QB+ over 90. Purdy then backed that up with a 95.7 (A) in 2023 and arguably could have been the MVP.
For the 2024 season, Purdy finished fifth in the league in overall EPA/DB (0.17) and fourth when playing under pressure (-0.08 EPA/DB) while sitting sixth when playing from a clean pocket (0.33 EPA/DB). Despite all the injuries around him, Purdy still averaged 8.1 nYPA (third) and a 44.3% conversion rate on third downs (eighth).
His touchdown-to-interception rate of 1.7 was a disappointment, thanks largely to his TD rate falling through the floor from 7.6 as a rookie and 7.0 in 2023 to 4.4 this season. That is not entirely on Purdy, given all the 49ers’ injuries this season, but it does paint the picture that he’s a product of the players surrounding him more so than a truly elite QB.
It will be fascinating to see what happens in contract negotiations this year with Purdy and the 49ers. It’s hard to make the case that he doesn’t deserve to be paid like a top-10 quarterback right now, but Purdy may even believe he should be in the top five.
Stats like third down conversion rate and how you deal with pressure are critical for success. Purdy, ranking highly in both areas, projects well and is another reason he’ll be paid handsomely this offseason.
It’d be troubling to see Purdy’s yards per attempt drop under pressure. That would suggest he’s either not trusting what he’s seeing or his eyes are dropping due to pressure, leading to check-downs. But that’s not who Brock is. If anything, he goes in the opposite direction, looking to heave a deep pass as a defender has a free run at Purdy. It’s a strong quality to have for a quarterback.
Purdy kept numerous plays alive during the year. Mobility is a must at quarterback, and the 49ers starter finished seventh in the NFL in scrambles and ran for the sixth-most first downs. Your offense is in good hands when your quarterback creates nearly two possessions per game with his legs.
It’s easy to forget that his 2024 season was without the best receiver on the team and one of the best in the NFL. When Purdy had Brandon Aiyuk, the results spoke for themselves.
