What to expect when the 49ers have the ball: How will Brock Purdy react to the pressure?

We’re finally here. We can talk about the product on the field. No more debating whether the 49ers will pay their star edge rusher. That happened. We can even focus on the starting quarterback, after the team traded their third-stringer to Dallas.

The Pittsburgh Steelers host San Francisco on Sunday. The last time these two teams met was in September 2019, when the Niners squeaked out a 24-20 home victory. This time around, the road team is fresh off an NFC Championship loss, while the home team needed a four-game winning streak to finish the season one game above .500.

So this should be a cakewalk for Kyle Shanahan, right? Not so fast. As a home underdog, Mike Tomlin is a god-like figure. The 49ers are currently 2-point favorites on DraftKings SportsBook, with the total on the game set at 41.5.

Tomlin is 13-4-3 against the spread as a home underdog, and he’s won 12 of those 20 games outright as a home underdog. Dating back to 1970, no head coach has a better record against the spread or straight up than Tomlin, with a minimum of 20 games.

And if you’re wondering whether Tomlin accomplished these figures earlier in his career, he’s 7-1-1 as a home underdog since 2020.

Let’s get into the matchup between one team that spent all offseason full of distractions, and another that’s been trending in the right direction.

What to expect when the 49ers have the ball

When you’re looking at year-over-year metrics, stats like completion percentage, passing from the pocket, and throwing without pressure are stable from year to year. We’ve seen for over a handful of years how open Shanahan’s offense gets wide receivers.

But other stats, like passing under pressure, are fickle from year-to-year. There are still plenty of folks outside the 49ers building who still question whether Brock Purdy is “the guy” for this team moving forward. That’s despite last year’s success and everything everyone in the organization has said about the second-year quarterback this offseason.

A few weeks ago, I compared Purdy’s numbers to Jimmy Garoppolo’s, in an attempt to paint a picture of how the two performed in specific categories:

For Purdy to be listed no lower than sixth is quite the tip of the cap. To me, it tells us that Purdy has a high floor, despite not having the physical tools as some of the top quarterbacks in the NFL.

The reason the 49ers averaged 30 points a game with Purdy under center and were the most efficient passing offense in the NFL was due to Brock excelling in ways that Jimmy failed to at the higher-variance metrics.

Purdy was 15th in EPA per play under pressure, compared to Garoppolo’s 27th ranking. The Niners saw an uptick in explosive play percentage on third downs, but, equally important, in passing success rate on first and third downs.

Sunday’s matchup against the Steelers will be one of if not the toughest of Purdy’s career — especially if you account for the environment. Brock and the 49ers go from facing seven defenses that averaged around an efficiency ranking of 20th, to a Pittsburgh defense who, from Week 12 on, finished 12th in EPA per play and seventh in success rate.

The next set of numbers will determine if Purdy is indeed here to stay. Because defenses will find ways to adjust. In 2022, Brock finished 34th of 37th in air yards during his time as a starter. An incredible 39 percent of Purdy’s throws were at or behind the line of scrimmage a season ago.

What was a strength of the Steelers defense last year? You guessed it. Pittsburgh, even without T.J. Watt for eight games, ranked No. 1 in EPA per play allowed on passes at or behind the line of scrimmage.

Watt’s return in Week 10 took a good Steelers unit to a borderline dominant one. They finished the final nine games of the season second in DVOA. The Steelers were 32nd without him.

If I’m Steelers defensive coordinator Teryl Austin, every rep that Watt takes against Trent Williams is a wasted one. Per Sports Info Solutions, Colton McKivitz has allowed a 7.5 percent career pressure rate as a tackle. That would have been the fifth-worst mark among all tackles in 2022.

Pittsburgh generated pressure at a 35 percent clip a season ago with Watt on the field. For reference, San Francisco finished the year with a 23 percent pressure rate, which ranked 11th. No team finished higher than 26 percent. Calling him dynamic is an understatement. Watt is a game-changer that the 49ers must be aware of at all times.

What I’m most interested in seeing on this side of the ball is how Purdy is affected by the pressure. Because it’s going to happen. Last year, Purdy’s accuracy took a 26 percent dip when pressured.

Is it as simple as one of the YAC-bros consistently breaking tackles, which keeps the 49ers ahead of the chains? We know Shanahan will put Purdy in a position to succeed. And while Purdy showcased the ability to make plays outside of structure as a rookie, he didn’t have Minkah Fitzpatrick lurking on the other side of the ball.

This feels like a game where we get a heavy dosage of Deebo Samuel and Christian McCaffrey. Deebo running crossing routes and McCaffrey in 1-on-1 situations against the Steelers linebackers.

Pittsburgh’s depth chart has an “or” designation for their starting inside linebackers. There’s Cole Holcomb — who missed most of the season after injuring his foot in October 2022 — and newcomer Elandon Roberts. Who is the “or,” you ask? None other than former 49ers legendary linebacker, Kwon Alexander.

Neither of the three stand a chance in a 1-on-1 situation against McCaffrey. To be fair to them, asking a linebacker to cover McCaffrey is a suicide mission. During training camp, McCaffrey consistently got the best of Fred Warner — a player almost unanimously considered the best coverage linebacker in the NFL.

You’d love to see Brandon Aiyuk give rookie cornerback Joey Porter Jr. a few “welcome to the NFL moments,” but it’s the other side that’s just as intriguing.

Patrick Peterson quietly had a stellar season with the Vikings last year. He only allowed two touchdowns, and had five interceptions to go with 11 pass breakups. Peterson will sit on routes and try to anticipate what the 49ers will run. One way to combat his aggressiveness is with a double move.

Does Shanahan trust his offensive line to hold up and give Purdy time to find a receiver down the field? I’d test Porter Jr. and Peterson deep at least once a quarter to keep them honest.

The Steelers were also inside of the top 10 after Watt returned in rushing EPA and success rate allowed. Thanks to several big plays, the 49ers were third offensively with Purdy under center in rushing EPA per play, and 11th in rushing success rate.

The Steelers drafted a defensive tackle in the second round this past season, but also added an edge rusher in the fourth round who made the rounds during the preseason. Nick Herbig finished with four sacks on a limited snap count.

Four keys to a 49ers successful offensive outing:

• Avoid Minkah Fitzpatrick at all costs
• McCaffrey has 7+ targets
• Convert in the red zone at 60 percent or higher
• Move the Purdy’s launching point, so Pittsburgh can’t tee off

Win.