A native of Jacksonville, Florida, Theus attended Bolles School where he was coached by Corky Rogers. As a sophomore, he was part of a 12–1 Bolles Bulldogs team led by running back Jawan Jamison that defeated Tampa Catholic for the 2009 FHSAA Class 4A state title. In his junior season, Bolles went undefeated through the regular season, only to lose 35–21 to Ocala Trinity Catholic in the Region 1-2B championship. In Theus' senior season, Bolles went 16–1 and beat Miami Washington for the second Class 4A state title in three years. After the season, Theus played in the U.S. Army All-American Bowl and was also named All-American by Parade and USA Today. Regarded as a consensus five-star recruit, Theus was ranked as one of the best offensive tackle prospects of the class of 2012, which also included Zach Banner, D. J. Humphries, and Andrus Peat. With scholarship offers from almost every major program in the country, Theus chose Georgia over Notre Dame, Florida, Texas, and Alabama.
College career
In his true freshman season at Georgia, Theus started all 14 games at right tackle. He was only the third true freshman to start at offensive tackle in a season opener for UGA since freshmen became eligible in 1973, and the first since Trinton Sturdivant in 2007. After a solid season in which Georgia ranked No. 1 in the SEC in yards per play, Theus was named Freshman All-American by CBSSports.com, The Sporting News, and Phil Steele. As a sophomore, Theus lost his starting job for stints when Kolton Houston returned to the team after having his eligibility cleared by the NCAA. Theus played in all 13 games of the season, starting eight of them. For his junior season, Theus was moved over to left tackle where he started in all 13 games. He was part of an offensive line that helped Georgia rush for 257.8 yards per game, which ranked first in the SEC. Theus earned AP Honorable Mention All-SEC after the season.
Professional career
Coming out of college, Theus was projected to be a fourth to sixth round selection. He was ranked the 14th best offensive tackle out of the 109 available by NFLDraftScout.com. He was invited to the NFL Combine and was able to complete all their drills and workouts besides the bench. He participated at Georgia's Pro Day and was satisfied with his combine number, only performing positional drills and the bench.
The San Francisco 49ers selected Theus in the fifth round, of the 2016 NFL Draft. On May 5, 2016, the 49ers signed him to a four-year, $2.59 million rookie contract with a signing bonus of $257,612. On September 13, 2017, Theus was waived by the 49ers.
On February 27, 2018, Theus was claimed off waivers by the New Orleans Saints. He was waived/injured by the Saints on May 7, 2018 and was placed on injured reserve. He was released on May 16, 2018.
