Phillips played at Oklahoma from 2011 to 2014. As a freshman in 2011, he was redshirted. As a redshirt freshman in 2012, he appeared in 12 games, recording 12 tackles. Phillips played in only four games his sophomore season in 2013 due to a back injury.[4] He had seven tackles and 1.5 sacks before the injury. Phillips returned from the injury in 2014.[5][6] He finished the year with 31 tackles and two sacks.
Phillips was drafted with the 52nd overall pick in the second round by the Miami Dolphins of the 2015 NFL Draft.[10] During his rookie year in 2015, Phillips played 15 games making 19 tackles, 2 sacks, and 4 passes defended.[11]
Phillips entered the 2018 season as a starting defensive tackle. However his playing time dipped as the season progressed, leading to an outburst on the sideline about his playing time in a Week 4 blowout loss to the New England Patriots.[12] On October 2, 2018, Phillips was waived by the Dolphins.[13]
Buffalo Bills (first stint)
On October 3, 2018, Phillips was claimed off waivers by the Buffalo Bills.[14]
On March 4, 2019, Phillips re-signed with the Bills.[15]
In week 5 against the Tennessee Titans, Phillips sacked Marcus Mariota three times in the 14–7 win.[16] Phillips emerged as a premier pass rusher for the Bills, racking up 9.5 sacks in the 2019 season.[17]
Arizona Cardinals
On April 6, 2020, Phillips signed a three–year contract with the Arizona Cardinals.[18]
In Week 2 against the Washington Football Team, Phillips recorded his first sack as a Cardinal, a strip sack on Dwayne Haskins which was recovered by teammate Chandler Jones during the 30–15 win.[19]
In Week 6 against the Dallas Cowboys on Monday Night Football, Phillips recovered a fumble lost by running back Ezekiel Elliott and forced a fumble on Elliott on the Cowboys' next drive of the game during the 38–10 win.[20] He was placed on injured reserve on November 19, 2020, with a hamstring injury.[21] He was activated on December 12, 2020.[22] He aggravated the hamstring injury in Week 14 and was placed on injured reserve on December 19, ending his season.[23]
On September 2, 2021, Phillips was placed on injured reserve to start the season.[24] He was activated on October 16.[25]
On March 16, 2022, Phillips was released by the Cardinals.[26]
Buffalo Bills (second stint)
On March 17, 2022, Phillips signed with the Bills on a one-year deal.[27] Following the year, Phillips revealed he had played the last few weeks of the season with a torn rotator cuff, and would undergo offseason surgery.[28]
Phillips re-signed with the Bills on April 6, 2023.[29] He was placed on the active/physically unable to perform list on July 25, 2023.[30] Phillips was activated on August 6, 2023.[31] He finished the season with 15 tackles, 2.5 sacks, and a career-high five passes defensed through 14 games and nine starts.[32]
On August 14, 2024, the Giants traded Phillips and a seventh-round pick in the 2026 NFL draft to the Dallas Cowboys for a 2026 sixth-round pick.[34] On November 5, 2024, Phillips was released by the Cowboys.[35]