He played for the Seahawks from 2016 to 2019, as well as brief stints for the Los Angeles Rams, Buffalo Bills, Las Vegas Raiders, and the New York Jets.

Jefferson attended Woodland Hills High School in Pittsburgh, Pennsylvania, where he played both football and basketball.

[16] In Week 14 of the 2017 season, Jefferson was ejected for being involved in a scuffle with some players on the Jacksonville Jaguars.

Jefferson attempted to climb into the stands in an effort to attack the fans, but was restrained by a team official.

[18] In the 2018 season, Jefferson had three sacks, 25 total tackles (15 solo), two passes defended, and one fumble recovery in 16 games and 12 starts.

[19] In Week 1 of the 2019 season against the Cincinnati Bengals, Jefferson recorded six tackles and sacked Andy Dalton twice in the 21–20 win.

He finished with 3.5 sacks, 26 total tackles (14 solo), three passes defended, and one fumble recovery.

[23] In Week 4 against the Las Vegas Raiders, Jefferson recorded his first career forced fumble, a strip sack on Derek Carr which he recovered himself, during the 30–23 win.

He finished with 4.5 sacks, 47 total tackles (17 solo), one pass defended, and two forced fumbles.

[30] He played in 17 games with three starts, recording 29 tackles, two passes defensed, and a career-high 5.5 sacks.