Under the scenario presented by Huizenga, Marino will report to the owner, while Spielman and head coach Dave Wannstedt will report to Marino.
The promotion of Spielman ended a search that began after the Dolphins extended the contract of Wannstedt but stripped him of his authority over personnel decisions.
The Dolphins interviewed seven candidates over the last two years: Spielman, Tampa Bay's Tim Ruskell, Seattle's Ted Thompson, former New Orleans GM Randy Mueller, former Green Bay GM Ron Wolf, former Dolphins wide receiver Paul Warfield and Baltimore scouting director Phil Savage.
The idea of Marino becoming involved didn't surface until Friday when he dropped by Dolphins camp to pick up Super Bowl tickets and talked with Huizenga.
Marino accepted the job at 11 a.m. Monday and the Dolphins told Spielman he had been promoted early in the afternoon.
"We're ecstatic," said Huizenga. "We think it's the right thing for the Dolphins organization. I feel in my heart that it's a team game on the field and a team game in the office as well. We need two good teams to win and the name of the game for us is to win and nothing else really matters except, what does it take for us to win on the field?
"I have a little side agenda that I hope that Dan Marino can pick up his Super Bowl ring in this new position here."
For Marino, he said joining the Dolphins front office was just the next logical step in his career.
"It's been a dream of mine to get back into football," Marino said.
"I loved the competition when I was a player. I love everything about this place. To me, I'm back home again. ... I want to do whatever I can and whatever is necessary for me to do to help this team in any way I can, to be back to where we need to be. That is to win a championship, which I never won."
Marino will begin his full-time duties with the Dolphins after the Super Bowl, as he will continue his work with HBO and CBS until then.