The Giants designated Johnson (undisclosed) for assignment Tuesday.
Johnson recently sustained an unspecified injury at Triple-A Sacramento that kept him out of the lineup for a few days and took him out of the mix for a call-up, but he had since returned to action for the club and played in five games last week. Though he's healthy again, Johnson will end up losing his spot on the Giants' 40-man roster with San Francisco activating Mitch Haniger (forearm) from the 60-day injured list Monday. Johnson, 27, heads into DFA limbo with a career .148/.209/.213 batting line in 41 major-league games. He's put up an .820 OPS with seven home runs and 14 steals in 50 games this season at Triple-A.