He then transferred to Marshall where he spent 2 years playing for the Herd. While at Marshall, he posted 208 tackles, including 16.5 for loss and 7.5 sacks, with two interceptions, four pass breakups, two fumble recoveries and one forced fumble. He was named Conference USA Defensive Player of the Year in 2014.
On May 2, 2015, Hewitt signed with the Miami Dolphins as an undrafted free agent following the conclusion of the 2015 NFL draft.[2] He made his NFL debut on September 13 against the Washington Redskins.[3] On November 22, he made first career start against the Dallas Cowboys and posted his first career interception.[4] On January 3, 2016, Hewitt made a season-high six tackles and one pass breakup against the New England Patriots.[5] He finished his rookie season with 39 tackles and an interception.[6]
On December 4, Hewitt recorded his first career fumble recovery against the Baltimore Ravens. On December 17, he made his first career sack against the New York Jets.[7] A week later, Hewitt recorded a career-high nine tackles against the Buffalo Bills.[8] He made five tackles in the AFC wild card game against the Pittsburgh Steelers.[9]
On September 2, 2017, Hewitt was waived by the Dolphins.[10] On October 9, he was re-signed to the Dolphins' practice squad.[11] He was promoted to the active roster on November 22.[12]
New York Jets
On March 28, 2018, Hewitt signed a one-year contract with the Jets.[13] He played in 16 games with four starts, recording 39 combined tackles and 1.5 sacks.
On March 13, 2019, Hewitt re-signed with the Jets.[14]
In Week 1 against the Bills, Hewitt intercepted Josh Allen once as the Jets lost 17–16.[15]
In Week 2 against the Cleveland Browns. Hewitt recorded 8 tackles and sacked Baker Mayfield once in the 23–3 loss.[16]
In Week 11 against the Redskins, Hewitt intercepted a pass thrown by quarterback Dwayne Haskins in the 34–17 win.[17]
On March 25, 2020, Hewitt re-signed for a third season with the Jets.[18] He started all 16 games, leading the team with a career-high 134 tackles, along with 2.0 sacks, four passes defensed, and one interception.
Houston Texans
Hewitt signed with the Houston Texans on May 7, 2021.[19] He played in all 17 games with five starts, recording 60 tackles.
On March 30, 2022, Hewitt re-signed with the Texans, playing almost exclusively on special teams that season.[20] He re-signed to play a third season with the Texans on May 8, 2023 again only on special teams.[21]
Hewitt re-signed with the Texans on April 1, 2024.[22]