Johnson signed a minor-league contract with the Padres on Dec. 21.
Johnson elected free agency Thursday.
The Giants outrighted Johnson to Triple-A Sacramento on Sunday.
The Giants designated Johnson (undisclosed) for assignment Tuesday.
Johnson didn't play for Triple-A Sacramento in Saturday's 6-5 loss to Tacoma due to an unspecified injury, Andrew Baggarly of The Athletic reports.
San Francisco optioned Johnson to Triple-A Sacramento on Tuesday, Maria I. Guardado of MLB.com reports.
The Giants recalled Johnson from Triple-A Sacramento on Thursday, Maria I. Guardado of MLB.com reports.
Johnson was optioned to Triple-A Sacramento on Monday.
The Giants recalled Johnson from Triple-A Sacramento on Thursday, Alex Pavlovic of NBC Sports Bay Area reports.
The Giants reinstated Johnson (concussion) from the 7-day injured list Sunday and optioned him to Triple-A Sacramento.