The Pittsburgh Steelers ended the work week by adding defensive reinforcements, agreeing to a two-year, $11 million deal with veteran DL Sebastian Joseph-Day. What can he offer the trenches? As we’ve done for the team’s previous external signings, let’s break it down.
Run Defense/Tackling
Run defense is Joseph-Day’s calling card. It’s the primary reason why he was added. A wide body much bigger than the 299 pounds he was listed at coming out of college but still having long, 34.5-inch arms, he’s a stout and square body to plug the run.
He’s difficult to move out of gaps and holds the point of attack well. Against over fronts, he dominates tight ends like you’d expect. Against Arizona, he is on the left side between No. 87 and 70. Against the Chargers, he is between the right tackle and tight end, wearing No. 69.
He’s not just winning the “easy” matchups. He plays with a strong base and tight hands. Joseph-Day handles and splits combo blocks/doubles well. He’s not making all the tackles here, but the important thing he’s achieving is keeping his linebackers clean. An unblocked linebacker is a happy linebacker.
He’s on the right side in the first clip between left guard and left tackle. He’s shaded inside of the right tackle in the second clip, and between right guard and right tackle in the final clip.
Joseph-Day is able to key the ball and shed, too. Between left guard and center in the first clip, and right tackle and tight end in the second.
Most often, he’s two-gapping like an old-school lineman. But he can also get upfield and disrupt, too. Joseph-Day has an acceptable get-off to fire through a gap. Between right guard and right tackle below.
He must more consistently be able to shed and plays a little too chest-to-chest for his length. His effort against the run is acceptable, he chases hard backside versus zone runs, but it’s not the fanatical level typical of a Steelers’ defensive lineman.
Overall, he is a strong run stopper who plays out of a four-point stance, both hands down, which just reminds of his mindset to stop the run.
PFF charged him for four missed tackles. Not a great figure, but it’s a small sample size that offers too much noise to make anything out of. On the whole, no issue with his ability to tackle one he actually gets hands on.
More positively, he was credited with 28 stops (presumably, all against the run). That ranked tied for 20th among defensive linemen last season. Of the Top 20, only one player – Denver’s Eyioma Uwazurike – played fewer snaps than Joseph-Day. On a percentage basis, his mark was very good.
Pass Rush
Joseph-Day’s best rush move is his bull. He’s quick enough off the line with a good punch and enough power to collapse the pocket against interior offensive linemen. This was the best rush I watched.
Granted, it’s against a mess of a right guard with miserable technique, the Chargers’ offensive line was a mess, but Joseph-Day takes advantage by running him into the pocket and finishing with the sack. One of two he had in 2025.
Another example against left guard.
But Joseph-Day lacks bend of flexibility to threaten the edges. He showed a club/rip early in the season against Arizona versus a center back block, but those moments were few and far between. His bull is inconsistent and often has a “slow burn” to it, taking time to get a push.
He can’t always shed, either. Joseph-Day lacks moves off his bull and his impact is often minimal when he’s attacking half-man.
Working on N0. 77 in the first clip (he gets a push but can’t find the QB), and the Chargers left guard in the second.
He was occasionally used on rush stunts and has some experience looping and containing.
Usage
Per PFF’s charting, Joseph-Day primarily played from the B-gap and out last season, Meaning, three-tech or defensive end (head up on the offensive tackle or shaded outside of him). Without charting it the way they do, it felt like he played more over the A-gap than the handful of snaps he was credited for. Still, especially later into the season, he played more defensive end.
In Pittsburgh, that’d make him the backup to defensive ends Cam Heyward and Derrick Harmon.
Early in his career, Joseph-Day played far more as an interior plugger. His skillset gives him the ability to do both. His work in the B-gap offered his best tape.
Because of his pass rush limitations, he was often removed on obvious passing downs. Jeffrey Simmons was Tennessee’s pass rushing lineman.
During each of his two years with Tennessee, Joseph-Day logged under 500 of the defense’s snaps. That was just about half.
Final Thoughts
Sebastian Joseph-Day is a veteran and plugger against the run. He’s strong with good length and difficult to move off his spot. He shows moderate burst off the ball and can go forward to fire into gaps, though he most-often two-gaps, or create power on his bull rush. Though primarily playing B-tech and wider, he’s versatile enough to play up and down the entire defensive line.
He’s most likely to backup and rotate behind Heyward and Harmon. But a new coaching staff may shift around roles and responsibilities, and it’ll be curious if Joseph-Day, Yahya Black, or someone else gets a look at nose tackle. Reasonably, one of them two should be the answer.
Pittsburgh’s defensive line depth hadn’t been good enough for the past several seasons. Isaiahh Loudermilk and Logan Lee seeing even some playing time wasn’t palatable, and too often one injury stretched the group too thin. Harmon missing five games in 2025, Cam Heyward out half the year in 2023. Pittsburgh should be five or six men deep here, and this move helps build that. Heyward, Harmon, Benton, Black, Joseph-Day is a really strong foundation, especially against the run.
The Steelers have underwhelmed here and facing run-minded teams like Baltimore and Cleveland has to be an area of emphasis. How do we beat our division is a central question any coach should ask.
Now, Pittsburgh could use a pass rushing/sub-package player. Black and Joseph-Day aren’t those guys. With the run defense bolstered, add in someone a little quicker and finesse as a sixth defensive lineman, and Pittsburgh could have a strong group top to bottom in 2026.
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