USC athletic director Mike Bohn suddenly resigned from his position Friday, effectively immediately. Bohn over the last four years has helped lead a turnaround for the Trojans, hiring head football coach Lincoln Riley and negotiating the program's move from the Pac-12 to Big Ten beginning July 1, 2024.

Though Bohn cited health concerns as part of his departure, four former or current USC employees recently raised concerns about Bohn's management during a recent top-to-bottom review of the athletic department conducted by an external firm, according to the Los Angeles Times.

The Trojans retained Gina Maistro Smith, a Philadelphia-based attorney from Cozen O'Connor, to conduct that review.

"In our singular pursuit of excellence, I am committed to ensuring we have the right leadership in place to achieve our goals," said USC president Carol L. Folt in a Friday statement. As part of that commitment and as we prepare to move to the Big Ten, we conducted a thorough review of the athletics department, including its operations, culture, and strategy. Having built a strong foundation over the last few years, now is the time for new direction grounded in our values and in expertise needed to fulfill our aspirational vision for Trojan athletics."

Bohn leaves the USC job after previously departing from the same role at Cincinnati to take the job out West. His ability to poach Riley, the highly regarded Oklahoma coach, allowed him to put his stamp on the athletic department. He also played a significant role in USC and nearby rival UCLA departing the Pac-12 for the Big Ten, a move that will come to fruition in about 13 months.

"In moving on, it is important now that I focus on being present with my treasured family, addressing ongoing health challenges, and reflecting on how I can be impactful in the future," Bohn wrote as part of a statement to the Times.

The departure of Bohn, an athletic director at five different institutions across the last 25 years, leaves USC with a key administrative vacancy as it prepares to make a difficult transition to the Big Ten.

"On behalf of the Trojan Family, I thank Mike for his contributions to our athletics department during a time of rapid transformation and growth," Folt said. "We will be announcing a transition team comprising both internal and external leaders in the coming days and will launch a national search for a new director of athletics shortly."

Bohn served as athletic director at Colorado from 2005-13 where he oversaw the Buffaloes' move from the Big 12 to the Pac-12. While he did not negotiate Cincinnati's move from the AAC to the Big 12, he did help set a standard of success for the Bearcats athletic department by hiring football coach Luke Fickell. Other stops for Bohn include Idaho and San Diego State. Before becoming an administrator, he played college football and baseball at Kansas.