The last time Johnson played in a game he had two interceptions, in the Jets preseason finale. He didn't dressed for the first three games.
Katnik was likely expendable because injured guard Pete Kendall is ready to return. Also, recently signed guard Wade Smith is ready to contribute.
Myers is one of the Jets best special teams. His release might be related to the team's desire to make third round pick Anthony Schlegel active. He was inactive the first three games.