DENTON, Texas (AP) North Texas athletic director Rick Villarreal is stepping down after 16 years, a tenure marked by persistent instability in the football program despite the building of a new stadium.

Villarreal said Monday the resignation was a ''mutual agreement'' with school President Neal Smatresk, who plans to hire an interim athletic director before deciding how to proceed with a search for a permanent replacement.

The upheaval in football started in 2006 when Villarreal fired Darrell Dickey after consecutive losing seasons followed four straight Sun Belt Conference championships and trips to the New Orleans Bowl.

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Villarreal hired Todd Dodge straight out of the high school ranks, a decision that backfired despite Dodge's 79-1 record in his final five seasons at nearby Southlake Carroll. It was the first such move for an upper-division school since Notre Dame with Gerry Faust in 1981.

Dodge was a dismal 6-37 before getting fired in the middle of his fourth season.

''Even when the work was challenging, it was gratifying,'' Villarreal said. ''I will miss being part of daily campus life, but will forever treasure memories of the experiences I've had at UNT.''

Dickey's firing a few weeks after he suffered a heart attack angered prominent Houston businessman and North Texas booster Jim McIngvale, a furniture store owner known in Southeast Texas as ''Mattress Mack'' because of his goofy radio and TV ads.

McIngvale demanded the school name an athletic facility after the fired coach or redirect his $1 million contribution to the music department.

Villarreal went with experience after the Dodge hire, and former Iowa State coach Dan McCarney took over in 2011, the same year that 30,000-seat Apogee Stadium replaced aging Fouts Field.

McCarney led the Mean Green to a 9-4 record and a Heart of Dallas Bowl victory in his third season in 2013, but the turnaround didn't last. That's now the only winning season in the past 11 years for North Texas.

Villarreal's second midseason firing in five years came last season when McCarney was let go after an 0-5 start. Fans turned on the athletic director as well, flying a banner that read ''Fire Rick'' over the campus last year.

Former basketball coach Johnny Jones made two NCAA Tournament trips in 11 seasons through 2012, but replacement Tony Benford has had four straight losing seasons since then. The women's basketball team has had 10 straight losing records.