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How Brock Purdy's growth, aggressiveness are evolving Kyle Shanahan's 49ers offense

4 October 2024Last Update :
How Brock Purdy's growth, aggressiveness are evolving Kyle Shanahan's 49ers offense

If an offense is ranked 31st in play-action rate, second in air yards per target and 31st in yards after the catch, you probably wouldn’t guess it’s Kyle Shanahan’s. But that is the situation for the 49ers.

It’s still an offense built on the run and the threat of the run, but quarterback Brock Purdy and Shanahan’s trust in him have changed how aggressively the 49ers attack the looks that defenses present. The 49ers’ offensive evolution isn’t like what Sean McVay and the Rams did in 2021 when they traded for Matthew Stafford. San Francisco is still running the ball at a very high rate — 25th in Cook Index (how frequently teams pass the ball on first and second downs in the first 28 minutes of regulation, before time remaining and score differential influence run-pass tendencies).

They’re still trotting out their 21 personnel (two backs, one tight end, two receivers) at a high rate (most snaps in the league), but they’re attacking defenses that match with heavier bodies with the pure drop-back game without play-action. With all the disguising that defenses do now, it seems Shanahan would rather have Purdy read out defenses than turn his back to them on a play fake.

Shanahan has progressively been moving in this direction since Purdy became the starter, but he’s cranked the dial all the way this season toward the pure drop-back game, which is an indication that he no longer believes Purdy needs the training wheels that play-action provides. But it’s not just the play calling that has changed. Purdy seems more confident in his physical abilities than ever a year removed from tearing his UCL in his throwing elbow in the 2023 NFC Championship Game.

He’s taking every opportunity to throw the ball deep and give his receivers the chance to make plays on 50/50 balls. In his first two seasons as a starter, Purdy ranked 28th in air yards per throw (7.7) among quarterbacks with at least 200 attempts. He’s averaging 10.6 air yards per throw this season. Some of his deep chucks go completely against what he’s taught — Shanahan has said that — but right now, he’s connecting.

For example, on his touchdown pass to George Kittle against the Patriots, he threw the ball into triple coverage. Kittle made an amazing catch. But it was more than simply Purdy giving his guy a chance.

In Week 2, the 49ers ran a similar concept against the Vikings in the red zone.

Week 2, 2:18 remaining in the fourth quarter, first-and-10

The concept is designed to create a rub to get the ball to Deebo Samuel underneath. This concept is designed to beat Cover 0 (man-to-man with no safety help inside) blitz, which the Vikings ran on this play.

Except, on Cover 0, defensive backs usually play with zone technique initially before locking onto their man. They’ll have their eyes on the quarterback for about two seconds in case of a quick pass. So when Purdy threw to Samuel, multiple defenders quickly converged on him to stop him for a 2-yard gain.

Week 4, 3:18 remaining in the second quarter, third-and-10

Back to Kittle’s touchdown catch against the Patriots. The defense was once again in a Cover 0 look. The 49ers ran almost the same concept but with Kittle inside and running the outbreaking route. The 49ers seemed to alter this play to draw the defense toward Samuel and get the ball to Kittle.

Again, the defense had eyes on Purdy initially, so it looked like the 49ers would create the space they wanted for Kittle outside.

However, the defense crowded Kittle and left Samuel wide-open underneath. Purdy seemed intent on getting the ball to Kittle, but the pressure might not have allowed him to look to Samuel anyway.

One of the weaknesses of Shanahan’s system is it can be predictable where the ball goes against the blitz. In some offenses, the quarterback is in charge of sniffing out pressures and changing the protection. In this system, the quarterbacks have “hot routes” built in on which a receiver will cut their route short against the blitz. This is a good way of keeping things simple for quarterbacks and allows them to play fast, but there are limitations. A smart defensive coordinator can game plan where he thinks an offense’s hot routes are.

From 2022 to 2023, Purdy averaged 7.3 air yards per throw against the blitz (58th among qualifying quarterbacks). This season, the 49ers seem to be taking a different approach. Purdy is averaging 10.9 air yards per attempt against the blitz (sixth highest in the league).

Week 4, 12:05 remaining in the third quarter, first-and-10

Here, the Patriots had an obvious safety blitz called with safety Jabrill Peppers lined up to the right of the formation. I’m not sure if the protection was changed or if Shanahan just called the perfect protection, but fullback Kyle Juszczyk motioned into the backfield and ended up blocking the blitz.

The route concept with a deep post and dig is usually run with play-action, but on this play, Purdy just dropped back.

Dropping back, Purdy saw the Patriots were disguising their coverage. It looked like they had a safety deep in the middle of the field, but after the snap, the free safety sat and covered the dig route. They were playing a form of Cover 2 with the corners playing deep halves.

This left the middle of the field open, and Samuel outran the corner. Purdy had time, made the right read and unleashed a deep ball to Samuel, who caught it for a 53-yard gain.

As the season progresses, I’m curious to see if Purdy takes more ownership over protections at the line of scrimmage to sort out pressures and block them rather than resort to throwing hot routes. The 49ers offense struggled against the Chiefs’ and Ravens’ pressure packages last season, so this sort of change could pay dividends against that type of defense.

Another reason Purdy is throwing so much deeper than he has is teams are playing more quarter coverage against them. According to TruMedia, the 49ers lead the league in the rate of quarter coverage faced. Quarter coverage is when there are four defensive backs deep, but there are different forms of it. Against the Patriots, the safeties were playing aggressively and closer to the line of scrimmage.

Week 4, 6:59 remaining in the first quarter, first-and-10

Early in the game, the 49ers came out in 21 personnel and the Patriots lined up six defenders on the line of scrimmage with both safeties close to the line of scrimmage to trigger against the run.

“(The Patriots) had six guys on the line of scrimmage a ton, which you can run the ball versus that, but if you just think you’re going to do it on every first down and second down, you’re going to be in a lot of third-and-longs and have some three-and-outs,” Shanahan said during his postgame news conference. “So you’ve got to mix it up and, you know, get them on their heels and make them play some other stuff. That’s why we had to throw some of those posts today — just the guys they had on the line of scrimmage, how tight their safeties were.”

In previous years, Shanahan may have tried to run the ball against these fronts or go to his classic play-action concepts. But with Purdy, he used the drop-back game. The 49ers hit a couple of deep passes against this type of coverage against the Patriots.

Week 4, 13:26 remaining in the fourth quarter, first-and-10

Here, the 49ers again came out in 21 personnel but lined up in a spread formation with Kittle outside before short-motioning inside. The 49ers had a classic quarters-beater concept: a 10-yard out with a deep post.

Purdy’s read is the safety lined up on Kittle. If the safety sits back and gives Kittle space, Purdy would hit Kittle breaking outside. But the safety triggered quickly on Kittle, leaving the middle of the field open and Jauan Jennings one-on-one with the corner.

Jennings didn’t create a ton of separation, but Purdy put the ball in the perfect spot and Jennings made a great contested catch.

“We caught them in quarters a couple of times,” Shanahan said. “On both those plays, their safeties were down tight and that’s where the ball has got to go (deep), and Brock made two good throws and both the guys came down with the play.”

Purdy has always had the quickness to get away from the pass rush and create second-reaction plays, but this season, he’s doing it more often and he’s making more aggressive throws when he breaks the pocket. Before this season, Purdy ranked 32nd in average time to throw (2.95 seconds) among qualifying quarterbacks. This season, he leads the league (3.31). We’ve seen Purdy use his legs in big games, including the NFC Championship Game when he scrambled five times for 48 yards. This isn’t new, but he appears to be pushing the boundaries of what he can get away with against NFL defenses. He’s doing it enough to where defenses have to invest resources when game planning for it, and that’s a major headache with all of the problems the 49ers offense already presents.

Another reason the 49ers have become so drop-back happy is the offensive line’s improvement. Trent Williams is a future Hall of Famer, and he still looks like the best left tackle in the NFL despite missing training camp. Left guard Aaron Banks looks like he’s improved. The biggest boost to this offensive line has been rookie right guard Dominick Puni, a stalwart with inside run blocking and pass blocking. Right tackle Colton McKivitz is a much better run blocker than pass blocker, but if you have one leaky area on your line, it’s easier to scheme around it.

The 49ers are tied for eighth for most total pressures allowed, but Purdy is at fault for some of these pressures because he’s trying to create plays. According to Pro Football Focus, Purdy ranks sixth in pressures charged to the quarterback. Last season, he ranked 20th in the same metric. Many top quarterbacks typically rank in the top 10 in this category because they are holding the ball and trying to create big plays rather than checking down. There are also bad quarterbacks who rank highly on this list. As long as quarterbacks are creating enough positive plays to justify holding the ball, there is no problem with this approach, but it’s a line that has to be tread carefully, especially because Purdy isn’t an elite athlete.

“Just the more he’s gotten comfortable and the more when something isn’t there he doesn’t try to force the perfect play, he just doesn’t hesitate and he breaks (the pocket),” Shanahan said.

The 49ers have mitigated the loss of Christian McCaffrey as a runner because Jordan Mason has been a revelation, but they miss McCaffrey’s ability as a receiver. Receiver Brandon Aiyuk is also having a slow start after his offseason holdout. Kittle and Samuel each missed a game due to injury. Through it all, Purdy has played his best football and the 49ers offense ranks seventh in DVOA. The defense is no longer elite because of the talent drain caused by the salary cap, so the offense will have to continue to lead this team.

That talent drain will eventually get worse when Purdy gets a massive quarterback deal. But with Purdy’s improvement this season and the offense’s evolution, he’s giving the franchise hope it’ll be in the right hands as the offense becomes more dependent on him and less dependent on play-action and yards after the catch.

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(Top photo: Alika Jenner / Getty Images)

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