EUGENE — After more than a decade of unprecedented success and regular NCAA Tournament appearances, Jim Moore is no longer the volleyball coach at Oregon.

Moore will officially retire May 15, though he will immediately step away from the program he led for 12 years, the school announced in a news release Wednesday night.

Without elaboration, the statement from Oregon said, "Coach Moore and the UO have come to realize that his coaching style is mismatched with the standards of the University of Oregon athletic department. He has acknowledged that his coaching style may have been viewed negatively by some student-athletes and for that he is sorry."

It was an unceremonious end for Moore, who leaves as the winningest coach in Oregon history. Also gone is assistant coach Stacy Metro, Moore's wife, who doubles as the head coach for the beach volleyball team.

Oregon associate head coach Matt Ulmer has been named interim head coach. Ulmer has been an assistant with the Ducks for the last three seasons.

Moore said he couldn't comment further when reached by phone Wednesday night, and Oregon officials denied The Register-Guard's request to speak with Ulmer and current players.

However, in a copy of a letter written this week to university president Michael Schill and obtained by The Register-Guard, several former players suggest Moore is being unfairly forced to resign amid accusations of mentally abusive behavior toward his players, accusations they say don't reflect the coach they know.

"His tenure has made me proud to refer to myself as an Oregon volleyball student and athlete," wrote Kristen (Forristall) Rott, in a letter co-signed by 17 former players, including all-Americans Liz Brenner, Sonja Newcombe and Martenne Bettendorf and eight members of the 2012 team that played for the national title.

Rott, whose senior season was 2008, described Moore as "an excellent coach, man of integrity, and educational leader."

"(His) student-athletes learned discipline, accountability, leadership, respect, self-worth, confidence, and courage," wrote Rott, now a teacher and volleyball coach at Wilsonville High School. "His character, his integrity, his work ethic, nor his intentions toward the University of Oregon have been called into question until now."

At least one player from every year of Moore's Oregon career signed the letter, with the exception of anyone from the 2016 team, which went 21-10 and advanced to the second round of the NCAA Tournament before losing to No. 17 Michigan in four sets.

Rott suggested it is the current players who have rallied against Moore, and she was careful not to be dismissive of their complaints.

"The purpose of this letter is not to void their opinions," she wrote. "The opinions they express are real to them. However, I would like to give you additional opinions from more than one cohort of athletes. The purpose is to more accurately describe his character."

When asked about the letter and the allegations of abusive behavior, senior associate athletic director Craig Pintens said Oregon wouldn't comment.

Moore, 58, was 246-132 at Oregon since taking over in 2005, and 120-110 in Pac-12 matches. He is under contract through Jan. 31 at an annual rate of $175,000.

After Moore's first year resulted in his only losing season at Oregon, the Ducks went 17-12 the following campaign for their first winning season in 15 years. They made the NCAA Tournament and ignited the most successful era of volleyball in school history.

Oregon's best season under Moore came in 2012, when the Ducks defeated Nebraska in Omaha to reach the Final Four, then knocked off top-ranked Penn State in the national semifinals before getting swept by Texas in the national championship match.

The Ducks also made regional semifinal appearances under Moore in 2007, 2008 and 2014.

Overall, Oregon played in the NCAA Tournament 10 times in 12 seasons under Moore, who has a career record of 598-288 in 28 years.

Moore came to Eugene in 2005 with a reputation as program builder after successful stints at Texas and Kansas State, as well as a 173-63 record and one national title during two different stints at Division II Northern Michigan.

He was hired by Oregon to lift the program out of a miserable slump.

The Ducks hadn't had a winning season in 14 years and their previous two coaches, Cathy Nelson and Carl Ferreira, had gone 86-209 overall and 13-167 in the then-Pac-10 over 10 seasons.

After joining the conference in 1986, Oregon had a winning record in Pac-10 play three times in its first four years. But the Ducks didn't accomplish the feat again until the arrival of Moore, who quickly set the program on a dramatically different course.