Also a track star at Warner Robins, Nelson had a best of 11.15 seconds in the 100 meters and was part of the 4x100 relay team that finished in first place in the county.

[2][3] Nelson entered his first season at Oregon State as the nickel corner, eventually becoming a starter and starting the final nine games.

[7] On January 24, 2015, Nelson appeared in the 2015 Senior Bowl and recorded four tackles as part of Tennessee Titans head coach Ken Whisenhunt's North team that defeated the South 34–13.

He attended pre-draft visits with the Pittsburgh Steelers and Detroit Lions and was considered one of the most underrated prospects in the upcoming draft.

[18] On October 11, 2015, Nelson made his professional regular season debut in the Chiefs' 36–21 loss at the Cincinnati Bengals in Week 4.

Throughout training camp, Nelson competed to be a starting cornerback after Smith departed for the Oakland Raiders in free agency.

On January 25, 2017, Nelson started his first career playoff game in the AFC Divisional Round against the Steelers and made five combined tackles as the Chiefs lost 18–16.

1 starting cornerback on the Chiefs' depth chart after the team traded Marcus Peters to the Los Angeles Rams.

[29] Head coach Andy Reid named Nelson and Kendall Fuller the starting cornerback tandem to begin the regular season in 2018.

On October 7, 2018, Nelson recorded three combined tackles, deflected two passes, and made his first career interception during a 30–14 victory against the Jaguars in Week 5.

[33] Head coach Mike Tomlin named Nelson and Joe Haden the starting cornerback duo to begin the regular season.

[36] In Week 8 against the Miami Dolphins, Nelson recovered a fumble forced by teammate Mike Hilton on Mark Walton in the 27-14 win.

[37] In Week 15 against the Buffalo Bills on Sunday Night Football, Nelson intercepted a pass thrown by Josh Allen and returned it for 33 yards as the Steelers lost 17–10.

[42] During the 2023 Wild Card game against the Cleveland Browns, Nelson intercepted a pass off of quarterback Joe Flacco, and returned it 82 yards for a touchdown in the Texans' 45–14 win.