Diaz, who spent the past three seasons on Richt's staff as Miami's defensive coordinator before accepting the Temple head-coaching job on Dec. 13, spoke with Miami officials about returning shortly after Richt announced his retirement.
"Miami is home. The University of Miami is home. The U has truly been 'the job' for me since I first got into coaching," Diaz said in a prepared statement. "Having worked here over the past three years, I came to understand what it means to be part of 'The U' and came to appreciate the passion and commitment to excellence of all who proudly call themselves Canes. We will restore the football program to its place among the nation's elite and we will do it with hard work, dedicated coaches, and outstanding student-athletes."
Diaz had agreed to a five-year contract with Temple that included a $4 million buyout if he chose to leave for another position. After taking the Temple job, Diaz worked for the Owls through the early signing date but returned to coach for Miami in last week's New Era Pinstripe Bowl loss to Wisconsin. Diaz had been among Miami's top recruiters and was instrumental in a 2018 recruiting class that ESPN ranked No. 8 nationally.
"As excited as I am about staying home, I hate the way this unfolded with respect to Temple," Diaz said in a statement. "I was given a tremendous opportunity to lead the Temple program and I was actively engaged in doing just that when I woke up this morning. I never saw this coming; no one did. I do hope that the Temple players, administration and fans appreciate the uniqueness of this situation and the overwhelming pull to stay home."
In a statement issued later Sunday, Temple athletic director Patrick Kraft said: "We are disappointed that he is leaving, but wish him the best as he returns home."
Diaz, 44, is a native of Miami and the son of the former Miami mayor also named Manny Diaz. He attended Florida State and briefly worked at ESPN before beginning his coaching career at his alma mater. Diaz has twice served as defensive coordinator at Mississippi State and held coordinator posts at Texas, Middle Tennessee and Louisiana Tech before joining Miami in 2016.
Miami athletic director Blake James, asked at a news conference Sunday about Diaz being on campus, declined to comment, saying only, "I guess Manny is on his own schedule." James said he was surprised when Richt told him of his decision to retire Sunday morning.
"Manny is one of the nation's elite coaches and the Canes' family has already embraced him and his incredible work ethic over the past three years," James said in a statement. "He is absolutely the passionate and innovative leader that our program needs, and we will work together to build an incredible staff to move our program back into championship contention."
Players were told Sunday night, and were thrilled.
"I give this coach all my respect,'' Miami running back Camron Davis said.
It's the second time that Miami technically has hired Temple's coach away from the Owls. The Hurricanes brought in Al Golden from there in 2010, and eventually replaced him with Richt in 2015.
Information from The Associated Press was used in this report.