Prior to his NFL career, Fells played professional basketball in several countries and was then signed by the Seattle Seahawks in 2013.

He has also played for the Arizona Cardinals, Detroit Lions, Cleveland Browns, Houston Texans, and Tampa Bay Buccaneers.

[3] As a rookie on the Basketball League Belgium Division I team Leuven Bears in 2008–09, Fells wore the jersey #14 and averaged 9.3 points, 4.9 rebounds, and 1.5 assists in 33 games.

[9] After the LNBP season ended, Fells played nine games for Obras Sanitarias of the Argentine Liga Nacional de Basquet from March to April 2012 and averaged 6.9 points and 4.7 rebounds.

Fells entered training camp competing with John Carlson, Troy Niklas, and Jake Ballard to be a backup tight end.

He was named the fifth tight end on the Cardinals' depth chart to begin the regular season, behind Rob Housler, John Carlson, Troy Niklas, and Jake Ballard.

[16] During a Week 15 12–6 road victory over the St. Louis Rams, he made his first NFL reception on a six-yard pass from Carson Palmer.

[17] In the regular-season finale against the 49ers, Fells caught a 24-yard pass for his longest catch of the season and finished the 17–20 road loss with two receptions for 39 yards.

[20] During the Wild Card round against the Carolina Panthers, Fells scored his first NFL touchdown on a one-yard reception from Ryan Lindley in the 27-16 road loss.

[22] During a Week 6 25–13 road loss to the Pittsburgh Steelers, he had a nine-yard reception before suffering a shoulder sprain that kept him out the next two games.

[24] In the postseason, Fells caught four receptions for 50 yards and a touchdown before the team lost to the Panthers in the NFC Championship Game.

[30] He entered training camp competing with Cole Wick, Khari Lee, and Michael Roberts to be the backup tight end.

Ebron struggled with drops in the first half of the season, and Fells saw increased snaps and eventually started in place of him.

[44] In the postseason, he had seven receptions for 59 yards and a touchdown before the Texans lost to the Kansas City Chiefs in the Divisional Round.