Purdy is back for Sunday's rematch in Philly and has the attention of the Eagles' new DC, Sean Desai.
"Brock's playing at a high level. Really efficient with the ball," Desai said on Tuesday, via the official transcript. "Getting the ball out with rhythm and timing to his receivers. I think they do a good job mixing the run and pass. And Brock really runs that offense really well. And he's feeling really comfortable doing that."
Heading into Week 13, Purdy leads the NFL in completion percentage (70.2), passing yards per attempt (9.4) and passer rating (112.3). Purdy is averaging 0.99 yards more per pass attempt than the next closest player (Tua Tagovailoa, 8.4), the sixth-largest difference between first and second since 1970.
Purdy benefits from playing in a cushy offense with oodles of surrounding talent -- Christian McCaffrey, Brandon Aiyuk, Deebo Samuel and George Kittle. Still, the second-year quarterback has also lifted the operation above previous Kyle Shanahan operations with his ability to avoid sacks and make plays when the structure breaks down.
"He's slippery. He's a little bit quick and can be evasive in the pocket," Desai said of Purdy. "And he keeps his eyes up field and is able to target some explosives downfield that way too. We will have to have a good plan corralling him and getting tight to some of these routes so we can contest some of the throws that they throw."
Desai was a defensive assistant in Seattle last season when Purdy made his ascent up the depth chart. The Seahawks faced Purdy once in the regular season and once in the playoffs, losing both.
Taking over for Gannon, Desai's defense has been mostly middling through 11 games. The rush-D has been stellar (second-fewest yards allowed on the ground), but the passing D has been ripped up, partly due to injuries on the back end. The crew sits in the teens in most relevant stats and tied for 12th in sacks (after leading the league last season).
The 49ers have been adamant that last year's NFC Championship Game would have gone differently if Purdy had stayed healthy. Given how the Niners offense could barely function after Josh Johnson was also knocked out with a concussion, Desai was asked if last year's tape was helpful.
"We look at everything. And that's our job as coaches to make sure we're prepared for everything and try to do our research and digging and trying to find everything," he said. "They still have to play some offense and they're still trying to go win that game. We do, we look at everything."
One side factor to Sunday's contest: The Eagles defense is coming off a 92-play day in the thrilling OT Week 12 win over Buffalo. The Niners had extra rest days after winning on Thanksgiving night in Seattle. That dichotomy could come into play for Desai's unit as it attempts to corral a steamrolling 49ers offense.