FRISCO, Texas -- Eighteen years after he last served as the Dallas Cowboys' defensive coordinator, Mike Zimmer is expected to be back in that role, a source confirmed.

Zimmer replaces Dan Quinn, who left to become the head coach of the Washington Commanders after a three-year run as the Cowboys' defensive coordinator.

Zimmer, 67, was a Cowboys assistant coach from 1994-2006. Starting as a defensive assistant, moving to defensive backs in 1995, the last year Dallas won a Super Bowl, and serving as the coordinator from 2000-06 under two different head coaches, Dave Campo (2000-02) and Bill Parcells (2003-06).

NFL Network first reported the deal between the Cowboys and Zimmer was expected to happen.

From 2014-21, Zimmer was head coach of the Minnesota Vikings, compiling a 74-59-1 record that included three playoff appearances. His time in the NFC North made him more familiar with Cowboys coach Mike McCarthy, then the Green Bay Packers head coach.

Zimmer will inherit a defense that includes two finalists for the Defensive Player of the Year in edge rusher Micah Parsons and cornerback DaRon Bland, who led the NFL in interceptions with nine and returned a record five for touchdowns. Cornerback Trevon Diggs is returning from a torn anterior cruciate ligament in his left knee but was signed to a five-year, $97 million contract last summer.

There are questions along the interior defensive line and linebacker, but the Cowboys were ranked fifth in yards per game (299.7) and points per game (18.5) in 2023. They were exposed, however, in losses to the San Francisco 49ers and Buffalo Bills in the regular season and gave up 48 points in the wild-card loss to the Packers.

Zimmer has a solid reputation inside the NFL, having served as the coordinator for the Atlanta Falcons and Cincinnati Bengals before taking over in Minnesota. While he has mostly worked in a 4-3 defense, he was the Cowboys' coordinator when they transitioned to the 3-4 under Bill Parcells in 2005 after the drafting of DeMarcus Ware, Marcus Spears, Kevin Burnett, Chris Canty and Jay Ratliff.

His scheme versatility is viewed as a plus.

Zimmer is the third defensive coordinator McCarthy will have in five seasons. Mike Nolan handled the job in 2020 but was replaced by Quinn after the Cowboys gave up a franchise-record 473 points. Quinn oversaw a defense that led the NFL in takeaways in 2021 and '22 while helping the Cowboys to three straight 12-5 seasons and three playoff trips.

The Cowboys also interviewed former Commanders head coach Ron Rivera, their defensive line coach Aden Durde, New York Jets safeties coach Marquand Manuel and had talks with former Buffalo Bills and New York Jets head coach Rex Ryan, who is now an ESPN analyst.