Chiefs Rookie R Mason Thomas Flashes Glimpses of Potential in Preseason Opener

Defensive end R Mason Thomas showcased his tremendous athleticism and speed off the edge in his debut with the Chiefs.

Jul 29, 2026; St. Joseph, MO, USA; Kansas City Chiefs defensive end R. Mason Thomas (51) walks down the hill to the practice fields during training camp at Missouri Western State University. Mandatory Credit: Denny Medley-Imagn Images | IMAGN IMAGES via Reuters Connect

Several Chiefs rookies flashed their talent yesterday in the team's preseason debut against the Los Angeles Rams. One of those first-year standouts was R Mason Thomas, a defensive end who was selected No. 40 in the 2026 NFL Draft.

While he didn't exactly stuff the stat sheet, Thomas showcased the talent that made him one of the best pass rushers in the SEC last season. He finished the contest with two assisted tackles, one quarterback hit, and one pass defended.

There were several plays where Thomas' explosiveness off the edge was on full display, with the most notable coming on the final play of the first half. After beating the right tackle on a speed rush, Thomas began charging at quarterback Ty Simpson at what appeared to be a million miles per hour. That's where his incredible 4.67 40-yard dash showed up.

R Mason Thomas called halftime pic.twitter.com/Lm8JyqJ2jd

— 📽️ Red Tribe Cinema (@ClayWendler) August 15, 2026

Standing at 6-foot-2, 241 pounds, most pre-draft scouts viewed Thomas as a player who would need to add more weight before becoming an every-down option. However, he made an impact in the run game, shedding blocks and forcing Rams tailbacks to avoid him at all costs.

We even saw some examples of Thomas bull-rushing L.A.'s offensive linemen. He may be regarded as a speed rusher, but Thomas told reporters after the game that he's no one-trick pony.

"I don't know why people regard me as a speed-rusher," Thomas said. "I do bull. I did bull at college, too. I guess it’s my stature, my weight, they classify me as speed."

R Mason Thomas on 3rd down in the RZ.

He's able to flatten his path to the QB by going to power and pressures at 8-9 yards. Ball is out immediately, but that's really nice to see. pic.twitter.com/IyZ6bjcjel

— Seth Keysor (@RealMNchiefsfan) August 16, 2026

There's still a difficult path for Thomas to earn consistent first-team reps this season, with him projected to back up Ashton Gillotte on the outside. Former first-round pick Felix Anudike-Uzomah has also had a strong camp and could be listed above him on the depth chart.

Still, Thomas has shown glimpses of his potential throughout practice sessions, primarily going up against second-year left tackle Josh Simmons. Thomas noted after the game that there were certain reps yesterday where he had to remind himself that not every snap will look like the ones he takes against his teammates.

"He's definitely a struggle to go against," Thomas said about Simmons. "He's definitely making us better. Iron sharpens iron, for sure. ... My teammates that we play in practice, they're a lot different from actually going against another opponent. It definitely put in perspective that you definitely have to hone in on the things that they do instead of what you're used to at St. Joe's."

Despite a crowded defensive end room, Thomas could still carve out a significant role with the Chiefs in 2026. The Chiefs haven't had an edge rusher with his combination of quickness and explosiveness for quite some time.

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