He attended and played football at Liberty High School, along with childhood friend and future Green Bay Packers teammate Jordan Love.

[5][6] Throughout training camp, Barnes competed to be a starting inside linebacker against Oren Burks, Ty Summers, and fellow rookie Kamal Martin.

On September 5, 2020, the Packers waived Barnes as part of their final roster cuts, but signed him to the practice squad the next day after clearing waivers.

He made his first career start and his professional debut in the Green Bay Packers’ season-opener at the Minnesota Vikings and recorded seven combined tackles (five solo) during their 43–34 victory.

[16] During the team's matchup against the Kansas City Chiefs in Week 9, Barnes made a season-high 9 tackles,[17] including one that prevented a touchdown by running back Darrel Williams.