Jeff Fish, the Falcons director of athletic performance, was released on Tuesday, the team confirmed.
The move is surprising because several players credited Fish with improving their strength, speed and agility.
Falcons tight end Tony Gonzalez credited Fish's kettle bell workouts with helping him to continue to play at a high level at age 36.
He also oversaw quarterback Matt Ryan's offseason workouts last season that were credited for his improve strength down the stretch.
Except for the 2009 season, the team has not been beset with a great deal of serious injuries on Fish's watch.
During the 2008 season, he was fined $2,500 by the league for his role in a sideline skirmish that involved Washington cornerback DeAngelo Hall.
A voice message was left for Fish.
Alex Marvez of Fox Sports, who's in Mobile, Ala. with Falcons officials, first reported the move and that A.J. Neibel is slated as Fish's replacement.
Neibel has been with the Falcons for two seasons. He has experince in Major League Baseball with the San Francisco Giants (2008-09) and the NFL with the Oakland Raiders (2003-09).
Fish had just completed his fourth season with the Falcons. He directed all aspects of the Falcons' physical development, injury prevention, rehabilitation and nutrition, among other responsibilities, according to his bio on the team's website.
Fish has 20-plus years of experience in the strength & conditioning and athletic performance.
Prior to joining the Falcons, Fish spent the previous four seasons (2004-07) as the head strength and conditioning coach of the Oakland Raiders.
He also worked at the University of Missouri (2001-03), the Kansas City Chiefs, the Tampa Bay Buccaneers, Tulsa, Kent State, Clemson and Western Michigan.
Fish, a native of Ithaca, N.Y., played wide receiver at Western Carolina.