Waiving Johnson clears 3.5 million in cap space, the amount he was due in the final year of his contract next season.
With the moves, the Raiders have rid themselves of three defensive backs from a year ago; Stanford Routt was released in early February.
REWIND: Raiders release CB Stanford Routt
Johnson, 32, played just four games in 2011, recording 14 total tackles, four passes defended and a forced fumble.
Eugene, 31, appeared in 14 games for the Raiders, recording four tackles and three fumble recoveries.