As a wrestler, in his senior year, Kline was the Ohio Division I (big-school) champion in the 285-pound weight class.

[5] Although he grew up just outside Cincinnati, Kline was a Cleveland Browns fan due to his father Rick's roots in northeast Ohio.

[6] As a senior, Kline primarily played left guard as he earned second-team all Mid-American Conference honors as the Golden Flashes had their best season in 40 years, going 11–3 overall, winning the MAC East title and playing in the MAC Championship Game, which they lost in double overtime to Northern Illinois University.

He had private pre-draft workouts with the New England Patriots as well as the New York Jets, Indianapolis Colts, Kansas City Chiefs, Cincinnati Bengals, Tennessee Titans and Oakland Raiders.

[9] He went undrafted, but after the draft ended on April 27, he was signed that day as a rookie free agent by the Patriots.

[12][13][14] He saw his first significant playing time in a December 15 game against the Miami Dolphins, when Patriots starting offensive lineman Nate Solder went down with an injury.

[15] Kline made his first start and played the entire game at left guard as the Patriots cruised to a 41–7 win over the Baltimore Ravens on December 22, 2013.

[18] Just days before the Patriots' final preseason game, on August 26 the perennial All-Pro Mankins was traded to the Tampa Bay Buccaneers,[19] a move expected to provide an opportunity for increased playing time for Kline, who started the final preseason game.

[20] However, after a subpar performance in that game, Kline was on the inactive roster for the regular season opener against the Miami Dolphins.

[26] Four days later on October 16 he started again at right guard, playing 57 snaps in a Thursday night Patriots win over the New York Jets.

[28][29][30][31] Kline made his first postseason start January 18, 2015 in the AFC Championship Game against the Indianapolis Colts following an injury to rookie center Bryan Stork, which resulted in guard Ryan Wendell moving to center and Kline at right guard.

Kline earned praise for his performance as the Patriots dominated the Colts 45–7 to advance to Super Bowl XLIX.

[41] After being inactive for the team's first two games, on September 25, Kline started at right guard in the Titans' 17–10 loss to the Oakland Raiders.

[43] In 2017 Kline started all 16 games at right guard for the Titans as the team went 9-7 and made the AFC Playoffs for the first time since 2008.