Early coaching career Although he initially did not want to become a coach like his father, he eventually decided to pursue coaching during his junior season at Valparaiso. Diebler was first hired by his former college coach
Homer Drew to be a student assistant with the team for the
2009–10 season. He was promoted to director of basketball operations for the
2010–11 season. The 2010–11 team won 23 games and was invited to the
2011 CIT tournament, where they lost to
Iona in the first round. He was promoted yet again to assistant coach for
Valparaiso to fill the spot of
Bryce Drew, who was promoted to head coach due to Homer Drew's retirement. The 2011–12 team finished 22–12, won the
Horizon League regular season championship, and made it to the
2012 NIT tournament, marking the second time that
Valparaiso had made the
National Invitational Tournament. They lost in the first round to
Miami (FL). In his second year as assistant coach during the
2012–13 season, Valparaiso went 26–8, won the Horizon League regular season championship for the second year in a row, and also were the
2013 Horizon League tournament champions. They made the
NCAA tournament for the first time in 9 years, where they lost in the second round to 3-seed
Michigan State.
Vanderbilt (assistant) Diebler was hired away from
Ohio State by
Vanderbilt to serve as an assistant coach, reuniting with former
Valparaiso head coach
Bryce Drew. With the help of Diebler,
the Commodores made the
NCAA tournament, losing to
Northwestern and finished with a 19–16 record. The next two seasons were losing seasons without postseason appearances, with records of 12–20 and 9–23. This decline of the program led to the coaching staff's firing at the end of the
2018–19 season. The one bright spot for Diebler during his time at
Vanderbilt, however, was in his recruiting efforts. He was the primary recruiter for 5–star
point guard Darius Garland, who committed to Vanderbilt on November 13, 2017.
Ohio State (assistant and associate) Diebler was hired back at
Ohio State on April 17, 2019, to serve as an assistant coach under head coach
Chris Holtmann,
Thad Matta's replacement. With the addition of Diebler before
2019–20 season, Ohio State went 21–10 during the regular season before their first conference tournament game against
Purdue was canceled along with the
2020 NCAA tournament was canceled due to the
COVID-19 pandemic. Prior to the 2022-23 season, Diebler was promoted to Associate Head Coach.
Ohio State 2023–24 Holtmann was fired on February 14, 2024, and Diebler was named the interim head coach for the Buckeyes. The Buckeyes went 5-1 under Diebler to finish the regular season, including a win over #2 Purdue in Diebler's first game as interim head coach. As the 10 seed in the
2024 Big Ten men's basketball tournament, Ohio State beat 7 seed Iowa in the second round, before falling to 2 seed Illinois in the quarterfinals. On March 17, Diebler was officially named Ohio State's head men's basketball coach. Selected as a 2 seed in the
2024 National Invitation Tournament, the Buckeyes beat
Cornell in the first round and 3 seed
Virginia Tech in the second round, before losing to
Georgia in the quarterfinals. ==Head coaching record==