The Texans fired a lot of coaches this January. One of which was defensive backs coach John Butler, who was recently hired by the Buffalo Bills in the same role. Under his watch last season the law firm of Kareem Jackson-Kevin Johnson-Johnathan Joseph was awful, underperformed, and the entire secondary was bad aside from some competent play from Andre Hal.
To replace him the Texans promoted Anthony Midget from assistant to the defenisve backs coach to the actual defensive backs coach. With his new title, and doing bigger things, they had a hole to fill.