Week 5’s matchup between the Seattle Seahawks and the San Francisco 49ers is an early game-of-the-year contender for the 2026 NFL season, and no one is under more pressure than new Seahawks offensive coordinator Brian Fleury. He spent the last seven years with the 49ers before taking over the reigning Super Bowl champions’ offensive play-calling duties this season. While flaws are hard to come by between the two NFC West juggernauts, the 49ers defense has already been exposed this season — and there’s one clear formation in which Fleury can gash them early and often on Sunday.
The 49ers defense ranks just 19th in expected points added per play (EPA/play) this season overall, while the Seahawks’ ranks second. The 49ers offense is first, though,
while the Seahawks is 15th. The 49ers offense against the Seahawks defense will be the elite-on-elite matchup between units. Those two units might play with such jarring physicality that they cancel each other out. The Seahawks offense against the 49ers defense is where the biggest opportunity for a surprise resides.
The 49ers are particularly bad against one offensive personnel grouping, 13 personnel. This is a three-tight-end set with just one running back and one wide receiver. The Los Angeles Rams popularized it last year, and run it at an extreme 30.8 percent rate so far in 2026. They reshaped their roster to prioritize wide receivers such as Puka Nacua and Jordan Whittington, who are interchangeable with tight ends. The Seahawks’ secret weapon in this scenario is tight end Elijah Arroyo.
The Seahawks have run 13 personnel 5.49 percent of the time, which is still good for middle of the pack (16th). The 49ers have faced it 16.67 percent of the time, third-most in the NFL. They’ve allowed 3.63 EPA against it, eighth-most in the league. Although facing the Rams in Week 1 inflated those numbers, they’re still struggling to identify and cover the inside tight end releases on pass plays. Look at what JP Acosta noticed in the play below.
This is the exact look every NFL offense is hoping to get out of 13 personnel with the over route being open. Gotta throw it pic.twitter.com/mORlo7rai9
— JP Acosta (@acosta32_jp) October 7, 2026
This could easily be Fleury’s first or second scripted play on Sunday. This concept looks perfectly suited to one player — tight end Elijah Arroyo. He’s a humongous, fluid athlete at the position and a nightmare to tackle after the catch. The 49ers went with a conservative Cover 3 call when the Denver Broncos showed this look last week. If quarterback Bo Nix had thrown the over route instead of checking down to running back RJ Harvey, he could have hit tight end Evan Engram in stride down the sideline for a possible 52-yard touchdown. Watch for Fleury to run an over route out of 13 personnel early in this game, and Arroyo to have a chance at his biggest professional play yet.
This article originally appeared on Seahawks Wire: How Brian Fleury can unleash Elijah Arroyo early against 49ers defense
