Nolan, who was free to negotiate and sign with other teams because his contract with the Dolphins had expired, spent two seasons as defensive coordinator in Miami.
The Dolphins finished ranked 15th in total defense in 2011, including ranking third in run defense.
Nolan, a former head coach in San Francisco, might not have remained in Miami anyway had he not taken the Atlanta job because there's no guarantee whoever the Dolphins hired as their new head coach would have kept him.
Nolan does leave with the respect of his former players, as evidenced by the tweet posted a short while ago by defensive end Kendall Langford.
"Atlanta have themselves a great guy and a hell of a defensive coordinator!" Langford wrote.
The big question on defense for the Dolphins moving forward will be whether they retain the 3-4 they ran under Nolan or whether they'll go to a 4-3 once they hire a new coordinator.
The status of the other Dolphins coaches remains up in the air until a new head coach is hired.
Interim head coach Todd Bowles has interviewed for the head-coaching vacancy in Oakland and is expected to interview for the defensive coordinator job in Minnesota.