Wannstedt said he made the change for a couple of reasons, including Fiedler's experience and his familiarity with the Jets.
"I know I know the offense," Fiedler said. "I know I could get guys in the right position. I know I could give guys little reminders in the huddle. Not to say that A.J. wasn't doing those things.
"My knowledge of the Jets as well, and their personnel even though they do have some new schemes this year. I think I'll be ready to get the team in the right position on each play."
Wannstedt refused to speculate about whether he would be inclined to remove Fiedler if he struggles early against the Jets, saying that he believed Fiedler would do a good job.
In other news:
-- As if the Dolphins offense didn't have enough problems, wide receiver Chris Chambers missed practice on Wednesday and he's listed as questionable for Sunday's game because of a knee injury.
-- The Dolphins signed running back Brock Forsey to replace the injured Lamar Gordon. Forsey played last season with the Chicago Bears and might suit up to back up Leonard Henry this Sunday if Sammy Morris (ankle) isn't ready to play.
-- Defensive tackle Tim Bowens' back continues to be a problem, and he already has been ruled out of Sunday's game.
-- Fullback Rob Konrad, meanwhile, practiced on Wednesday, but it's too early to say whether he'll be able to play on Sunday.
-- The Dolphins signed two players to the practice squad, cornerback Vontez Duff and linebacker Renauld Williams.