[9] As a top defensive tackle prospect, Billings chose to forego his senior season and would receive an invitation to the NFL Combine.

Fox Sports listed him as one of their top five biggest winners from the combine and his performance was perceived well overall by scouts for his display of raw strength coupled with exceptional quickness and speed for a man of his size.

[10] On March 16, 2016, Billings participated at Baylor's Pro Day along with Corey Coleman, Shawn Oakman, Spencer Drango, Xavien Howard, Grant Campbell, LaQuan McGowan, Jimmy Landes, and seven other teammates.

He was projected as a first rounder in multiple mock drafts by Pro Football Focus and NFL analysts Todd McShay and Mel Kiper Jr.[22] There were many speculations that ranged from his lack of height and size for his position and a possible knee injury.

[24] He competed with Domata Peko, Pat Sims, and DeShawn Williams throughout training camp for the starting nose tackle position.

Billings competed with Pat Sims, DeShawn Williams, and Josh Tupou throughout training camp for the vacant starting nose tackle position left by the departure of Domata Peko to the Denver Broncos during free agency.

[26] Head coach Marvin Lewis named him the backup nose tackle to Pat Sims to begin the regular season.

[27] He made his professional regular season debut in the Bengals' season-opener against the Baltimore Ravens and recorded one solo tackle in their 20–0 loss.

On November 24, 2017, Billings earned his first career start against the Tennessee Titans in place of Sims who had injured his calf the previous week.

[38] On September 15, 2024, Billings collected his first career forced fumble, using his helmet to knock the football out of the hands of Houston Texans running back Cam Akers.