He played his first game against Clemson and caught his first career touchdown, a 33-yard Hail Mary from quarterback Kiehl Frazier, against Louisiana-Monroe.

In December 2014, Coates decided to forego his senior season and declared for the 2015 NFL draft[13] and also graduated from Auburn University with a diploma in Public Administration.

NFL scouts at the Senior Bowl said they loved Coates' sudden cuts, superior speed and big, well-developed frame, and his potential makes him a possible future No.

Coates met with team representatives from the Baltimore Ravens after he had an impressive week of practice where he made multiple highlight reel catches.

Under Jacksonville Jaguars head coach Gus Bradley, Coates helped the South defeat the North 20–10.

On March 3, 2014, Coates opted to participate at Auburn's pro day along with Greg Robinson, Dee Ford, Chris Davis, Tre Mason, Cody Parkey, Jay Prosch, Quan Bray, and nine other teammates.

At the conclusion of the pre-draft process, Coates was projected to be a second or third round pick by the majority of NFL draft experts and scouts.

Head coach Mike Tomlin named Coates the fourth wide receiver on the depth chart to start the season, behind Antonio Brown, Wheaton, and Heyward-Bey.

[24] On September 27, 2015, Coates made his professional regular season debut in a 12–6 victory over the St. Louis Rams after he was inactive for the first two games.

[27] Coates made two receptions for 61 yards in the Steelers' 16–23 loss to the Denver Broncos in the AFC Divisional Round of the playoffs.

[28] Coates competed with Wheaton and Heyward-Bey for the starting wide receiver job after Bryant was suspended for the entire 2016 season.

[29] On September 12, 2016, he received his first career start against the Washington Redskins and finished the season-opener with two receptions for 56 yards in the Steelers' 38–16 victory.

[30] The following week, he earned two receptions for 97 yards and had the first rushing attempt of his career for a six-yard gain, as the Steelers defeated the Cincinnati Bengals 24–16.

[32] It was reported that he suffered a broken index finger and required stitches during the game against the Jets but was still activated for the following week against the Miami Dolphins.

[35] On January 22, 2017, in the AFC Championship, Coates made two receptions for 34 yards in a 17–36 loss to the eventual Super Bowl LI Champion New England Patriots.

[37] Coates competed with Bryant and rookie JuJu Smith-Schuster for the vacant starting wide receiver position left by the departure of Wheaton.

[40] Head coach Hue Jackson named Coates the fourth wide receiver behind Kenny Britt, Corey Coleman, and Rashard Higgins to start the 2017 season.

[54] He was released by the Elks after their final preseason game, along with 17 other players as the team trimmed down its roster ahead of the season.

[63] On January 21, 2025, Coates was hired as the head football coach at Columbia High School in Huntsville, Alabama.