On Wednesday, Fletcher wrote on Twitter that he had ''reached out'' to Haslett and ''apologized for the harm I caused him and his family. He didn't deserve to be treated like that.''
In a TV appearance in December, Fletcher called Haslett ''clueless'' and responsible for Washington's ''ineptitude'' on defense.
The linebacker retired after the 2013 season. Haslett was let go by the Redskins after last season.
Fletcher tweeted Wednesday: ''I let my personal frustrations get to me. `Haz' treated me great while we were together. We all played a part in our success & failure.''
He also tweeted an apology directed at Haslett's son.