Graveman was activated off the 10-day injured list Tuesday, Greg Johns of MLB.com reports.
The 29-year-old landed on the injured list in early August and was eventually diagnosed with a benign bone tumor in his spine, but he never gave up hope for a return to the field this season. Graveman opened the season in the Mariners' starting rotation, but he'll shift to the bullpen since his neck apparently proved bothersome in longer outings.