Besler was a four-year All-Conference player at Blue Valley West High School in Overland Park, Kansas.

Besler was named the 2004 Kansas City Star Metro Player of the Year, and an NSCAA High School All-American.

He helped Notre Dame gain four straight berths in the NCAA championship, including the program's first two trips to the quarterfinals in 2006 and 2007.

[4] In 2012, Besler anchored the top defense in MLS with Sporting Kansas City and helped the club win the U.S. Open Cup by converting his attempt after the game against the Seattle Sounders went into penalty kicks.

[9] On January 6, 2021, Besler signed as a free agent with Austin FC ahead of their inaugural season in MLS.

[11] On August 23, 2012, Besler was called up to the United States team by head coach Jürgen Klinsmann for a friendly against Mexico, but he did not appear in the match.

On June 2, Besler started as the United States defeated Germany[13] 4–3 in an international friendly played at RFK Stadium.

After being left off of the initial roster for the 2013 CONCACAF Gold Cup so that the team could evaluate other players, Besler was added to strengthen the squad after the United States qualified for the knockout round.

Following his strong performance in the World Cup, several European outfits placed offers and expressed interest in signing Besler, including Freiburg, Fulham and Sunderland.

He scored his debut national team goal on September 2, 2016, with an assist from Sporting Kansas City teammate Graham Zusi.