Walker was ejected for unsportsmanlike conduct with 7:24 left in Green Bay's loss after shoving a trainer attending to Lions running back D'Andre Swift.
"I want to apologize publicly about what happened Sunday night. I reacted off of my emotions again and take full responsibility of making another stupid decision. Since then I've questioned myself on why did I do what I did when the trainer was doing his job!! I was wrong!!" Walker posted in one of three tweets Monday morning.
It's the second time this season Walker has been ejected.
His first came on Oct.