Upton elected free agency after being optioned to Triple-A Norfolk on Friday, Ryan Divish of The Seattle Times reports.
Upton saw sporadic playing time over the last few weeks and will lose his spot on the active roster after Kyle Lewis (concussion) was reinstated from the injured list Friday. Upton hit just .125 with a homer, three RBI and two runs over 17 games with the Mariners but will attempt to seek out other options as a free agent.