He was a starter during the 2018 College Football Playoff National Championship game, where Alabama won in overtime over Georgia, 26–23.

[9] Throughout training camp, Wallace competed for a roster spot as a backup cornerback against Taron Johnson, Ryan Carter, Breon Borders, and Lafayette Pitts.

[10] On September 1, 2018, the Bills waived Wallace as part of their final roster cuts, but signed him to their practice squad the following day.

[11] On November 6, 2018, the Bills promoted Wallace from their practice squad to the active roster after releasing Phillip Gaines.

[16] Following an inconsistent start to the season, Wallace eventually saw his playing time reduced in favor of Kevin Johnson.

[17] In week 15, Wallace caught his first career interception against the Pittsburgh Steelers on Sunday Night Football, picking off Devlin Hodges to seal a 17–10 Bills victory in the final moments to help Buffalo clinch a playoff berth.

[18] In the regular season finale against the Jets, Wallace logged another interception off Sam Darnold, but suffered a sprained ankle on the play,[19] which kept him out of the Bills' playoff game against the Houston Texans.

[21] On April 2, 2020, Wallace was re-signed to a one-year contract by the Bills, regaining his starting position despite the team signing veteran cornerback Josh Norman.

[27] In Week 14 against the Steelers on Sunday Night Football, Wallace intercepted a pass thrown by Ben Roethlisberger late in the fourth quarter to secure a 26–15 win for the Bills.