The University of Arizona named assistant coach Russ Pennell as interim head coach, replacing the retired Lute Olson, after associate head coach Mike Dunlap turned down an offer to replace Olson.
"Obviously, when I woke up this morning, I didn't expect to be sitting in front of you," Pennell told reporters at a McKale Center news conference.
Associate head coach Dunlap and assistant coach Reggie Geary will remain in their current positions.
The move that makes Pennell interim head coach may be as stunning as Olson calling it quits. Pennell was most recently an AAU coach in Phoenix and a radio broadcaster for Arizona State. Before that, Pennell was on Arizona State's staff for eight seasons, but that didn't end well.
Pennell wasn't retained by ASU coach Rob Evans. According to multiple sources close to the ASU program, Pennell was not brought back primarily because of a disagreement with Evans on his job performance.
Pennell had been on Evans' staff at Ole Miss prior to coming with him to Arizona State.
"I may not be a household name, but I've been around this game 47 years and nine months," said Pennell, the son of a basketball coach. "I was born into a basketball family."
Dunlap, who ran the majority of Monday's practice at Arizona, was the head coach of two-time Division II national champion Metro State (Colo.) before working for the Denver Nuggets as an assistant coach for two seasons.
Multiple sources told ESPN said Dunlap was looking to secure a longer commitment as head coach of the Wildcats, but that Arizona was interested in a national search.
Dunlap was brought in at Arizona as an associate head coach to Olson, replacing Kevin O'Neill, who held the same title before he was named Olson's successor last December.
That plan was ultimately scrapped when Olson returned this season and O'Neill went to the NBA. He is now an assistant with the Memphis Grizzlies.
Pennell and Dunlap were added to the coaching staff last spring after the departures of assistants O'Neill, Josh Pastner and Miles Simon. Pastner joined John Calipari's staff at the University of Memphis.
Olson's abrupt announcement could lead to the Wildcats losing their three-player committed recruiting class. The weeklong early signing period begins Nov. 12.
Arizona could be headed toward an Indiana-like implosion if juniors Chase Budinger and Jordan Hill declare for the NBA draft in June.
Once Arizona athletic director Jim Livengood moves on to the business of conducting a national search, he is expected to reach out in some form to gauge the interest of Gonzaga's Mark Few and Pittsburgh's Jamie Dixon.
"This is a great job," Livengood said. "It's a great place to live. It's a great university. There will certainly be a number of people who think this is a great place to coach."
Livengood said the school is still negotiating a contract with Pennell.
The decision to promote Pennell comes one day after the 74-year-old Olson stepped down after 25 seasons with the Wildcats.
Livengood said he first learned of Olson's decision in a report on ESPN. He said Olson phoned him in the afternoon.
Olson is not believed to have spoken to his players since stepping down. Livengood said he met with the players.
"The kids are good," Livengood said. "They're resilient. But they're hurting right now."
Pennell has 23 days to prepare for the season opener against Florida Atlantic on Nov. 17, at home in the first round of the NIT Season Tipoff.
"You've got a group of kids sitting downstairs that have been rocked to the core, which shows their great love and admiration for the man they came here to play for, coach Olson," Pennell said. "But I also know from talking to those kids today that they're competitors, that they're Wildcats, that they want to carry on the great tradition that the University of Arizona has enjoyed over the last couple of years."
Arizona went 19-15 last season and earned the school's 24th consecutive NCAA tournament appearance, the nation's longest active streak.
Andy Katz is a senior writer at ESPN.com. The Associated Press contributed to this report.