Tillery was originally going to play offensive tackle as a freshman at Notre Dame in 2015, but it was later decided he would play defensive tackle.[3][4] That season, he played in 12 games with three starts and recorded 12 tackles and a sack.[5] As a sophomore in 2016, he started 11 of 12 games, recording 37 tackles. As a junior in 2017, Tillery started all 13 games, finishing the season with 56 tackles and 4.5 sacks.[6] He returned to Notre Dame for his senior year in 2018.[7][8]
Tillery was drafted by the Los Angeles Chargers 28th overall in the first round of the 2019 NFL draft.[12] As a rookie, he appeared in 15 games and made three starts. He had two sacks and 17 total tackles (nine solo).[13]
In Week 9 of the 2020 season against the Las Vegas Raiders, Tillery recorded a strip sack on Derek Carr that he also recovered during the 27–25 loss. This was Tillery's first forced fumble and fumble recovery in the NFL.[14] In the 2020 season, he had three sacks, 30 total tackles (19 solo), two passes defended, two forced fumbles, and one fumble recovery.[15] In the 2021 season, Tillery had 4.5 sacks and 51 total tackles (24 solo) in 16 games and starts.[16]
The Chargers declined the fifth-year option on Tillery's contract on May 2, 2022, making him a free agent after the season.[17] Tillery was waived on November 10, 2022.[18]
Las Vegas Raiders
On November 14, 2022, Tillery was claimed off waivers by the Las Vegas Raiders.[19] He finished the 2022 season with one sack, 18 total tackles (13 solo), and one forced fumble over 15 games and four starts with both teams.[20]
Tillery re-signed with the Raiders on March 17, 2023.[21] In an October 1 game against the Los Angeles Chargers, Tillery was ejected after a late hit on former teammate Justin Herbert.[22] In the 2023 season, he finished with two sacks, 31 total tackles (11 solo), and one fumble recovery in 17 games and six starts.[23] Tillery was released by the Raiders on March 13, 2024.[24]