When Bill Parcells decided to work for Jerry Jones, observers wondered how long their egos could coexist. Four years later, both emerged unscathed — and unfulfilled.

While their working partnership never had any public blowups, they failed in their bid to make the Dallas Cowboys Super Bowl champions again. They didn’t even win a playoff game.

The experiment ended Monday with Parcells retiring. He’ll be 66 this preseason and decided that after 19 years in the NFL, he’d had enough, especially after the exhausting way this past season ended.

The Cowboys were 8-4 and holding a two-game lead in the NFC East when the bottom fell out. They lost four of their last five, including the final three, culminating with a playoff loss in Seattle that was decided when Pro Bowl quarterback Tony Romo botched the hold of a short field goal with a little more than a minute left.

“I am in good health and feel lucky to have been able to coach in the NFL for an extended period of time,” Parcells said in a statement. “I leave the game and the NFL with nothing but good feelings and gratitude to all the players, coaches and other people that have assisted me in that regard.”

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"It's time," Parcells told the New York Daily News. "Physically, I can do it. I'm in good shape. Mentally, I just feel like it's time to stop. I know I'm stopping for good."

Parcells also told the Daily News that controversial Terrell Owens didn't cause his decision.

“It was my job to try and make it work,” he said.

Jones also released a statement, opening it with a reference to him and Parcells avoiding the bitter divorce he and his first coach, Jimmy Johnson, had in 1993.

“I’d first like to say that my respect and appreciation for Bill Parcells has only grown since the first day he joined the Dallas Cowboys,” Jones said. “Our relationship, both on the professional and personal levels, is something that I am grateful for and something that will continue on into the future. It is a relationship that was structured around the fundamental element of applying all of our joint resources, energy and efforts into winning and being successful in every aspect of the organization.”

Now what?

Jones will hire the seventh coach in team history and he’ll either lead the team to a Super Bowl title like Tom Landry, Johnson and even Barry Switzer — or he won’t, like Parcells and his two predecessors, Chan Gailey and Dave Campo.

Actually, Dallas’ first priority will be winning a playoff game, something that hasn’t happened since 1996.

Parcells got the Cowboys close, lifting them from 5-11 to the playoffs in his first year. After missing out the last two seasons, the emergence of Romo had the club rolling — and the coach fired up — until their flameout finish.

“I want to thank Jerry Jones and (team vice president) Stephen Jones for their tremendous support over the last four years,” Parcells said. “Also, the players, my coaching staff and others in the support group who have done so much to help. Dallas is a great city and the Cowboys are an integral part of it. I am hopeful that they are able to go forward from here.”

Known for a gruff demeanor and colorful quotes, Parcells leaves with the ninth-most wins in NFL history and a career record of 183-138-1. He won two Super Bowls with the New York Giants, got to another with the New England Patriots and led the New York Jets to the AFC championship game.