Hubie Brown retired as coach of the Memphis Grizzlies on Thursday because of health reasons.
"Unexpected health-related issues will not allow me to continue coaching the Memphis Grizzlies," the 71-year-old Brown said in a statement. "This situation was unforeseen and absolutely nonexistent at the beginning of the season."
Assistant coach Lionel Hollins was named interim coach, Grizzlies president Jerry West said. ESPN's Jim Gray reported that Mike Fratello is the leading candidate to replace Brown.
Brown was not available for comment Thursday. The team scheduled a news conference for Friday.
"This is an extremely sad day for me," West said in a statement. "This franchise is by far better from the leadership and guidance of Hubie Brown, and we will be forever grateful to Hubie."
Grizzlies spokeswoman Stacey Mitch said Brown did not have a serious illness but declined to comment further, referring all questions to Friday's news conference.
Brown retired one day after the Grizzlies lost to the Seattle SuperSonics 93-84 and slipped to 5-7, fourth place in the Southwest
Division. He made no reference to retiring after the game.
During the game, Brown was active, arguing with officials, calling out plays and checking on players when they were injured.
Brown was the oldest coach in the NBA when he returned to the league in 2002 after a 16-year break.
He was the coach of the Atlanta Hawks from 1976-81 and the New York Knicks from 1982-86. He took the Hawks to the playoffs three times, including when he was named NBA coach of the year in 1978, and the Knicks to playoffs twice.
In 1975, Brown led the Kentucky Colonels to the ABA championship.
Fired by the Knicks after starting 4-12 in 1986, Brown became a TV basketball analyst.
He returned to the league on Nov. 12, 2002, when he replaced Sidney Lowe after an 0-8 start with the Grizzlies in their second season after leaving Vancouver, where the franchise was founded in 1995. Brown went on to lose five straight games to start 0-13.
The Grizzlies went on to win a franchise best 28 games, before last year's 50-32 record and first playoff appearance. Brown received his second coach of the year award after last season and leaves as the winningest coach in Memphis history with a record of 83-85.
Brown finishes with a career NBA record of 424-495 and a total record of 528-559, including ABA games.
Indiana coach Rick Carlisle said Brown will be missed.
"What Hubie Brown has done for our league in the last two years has been great," Carlisle said. "He brought an injection of life into that Memphis franchise and made them a playoff team.
"He's been a great coach for a long time, but his contributions to our game the last couple of years have been momentous," Carlisle said.
Brown needed medical attention last Dec. 27 during a loss at Dallas. He insisted at the time he tripped getting up from the bench in the fourth quarter but was examined in the training room.
"When you're old, everybody gets excited," Brown said after the team's fourth game in six days. "I just stumbled. I'm fine, everything is fine."
There was little doubt Brown would return this year. He was given medical clearance and told The Associated Press before the season he had no hesitation coming back.
"No, none at all," he said at the time. "I feel fine."
While much is expected of Memphis, the team has been hampered by injuries and has not performed to the level it reached last season.
Hollins takes over as an interim coach for the second time. He first joined the Grizzlies as lead assistant in Vancouver during the team's inaugural season. He took over midway through the 1999-2000 season, guiding Vancouver to an 18-42 finish.
"Obviously I was saddened by it," Hollins said. "Coach Brown has done so much for this franchise and this organization, and the players that he developed and laid a strong foundation of winning, work ethic and discipline."
Grizzlies forward James Posey said before the season that Brown could have retired at that time without apologizing.
"He could sit back and have a couple of margaritas or something, but he chose to come back," Posey said. "That's why I love to be around him. He's not willing to give in."
Information from The Associated Press was used in this report.