Raiders owner Mark Davis released a statement on the decision, per Tom Pelissero of NFL.com:
“We appreciate Jack's effort in building the foundation of this team for the future. Thank you to Jack, his wife, Linda, and his daughter, Aubrey, for their important contributions to the Raiders and our local community in Oakland. We wish them all the best."
The move comes after Del Rio and the Raiders agreed to terms on a four-year contract extension in February after he helped the franchise secure its first playoff berth since 2002.
Despite all the improvements the Raiders made in 2016 prior to quarterback Derek Carr's season-ending fibula surgery, they took several steps back in 2017—especially on offense.
Although Carr was healthy and the Raiders bolstered their backfield by signing Marshawn Lynch out of retirement, the Silver and Black's once-vaunted attack was enveloped by a malaise following the offseason ouster of offensive coordinator Bill Musgrave.
During a 6-10 finish in 2017 that resulted in a third-place finish in the AFC West, the Raiders struggled under offensive coordinator Todd Downing, fueled by a mediocre passing attack and a ground game that lingered near the bottom of the NFL rankings all season despite the Raiders' big-money commitments to offensive linemen Kelechi Osemele, Gabe Jackson and Donald Penn.
Now in the market for a new head coach, the Raiders figure to be focused on finding a boss who can maximize the deep pool of talent they've collected on that side of the ball over the past few years.
If they can do just that, they should be able to make good on Carr's prime and regain the form that allowed the franchise to have legitimate Super Bowl aspirations in 2016.