Greenlaw (undisclosed) did not participate in Wednesday's training camp session, Cam Inman of The San Jose Mercury News reports.
Greenlaw had no injury listed since signing with the team in late March. The linebacker's unnamed issue comes with no context, so it is unclear how long he will be absent. If the 49ers' 2019 fifth-round pick remains off the field, Luke Gifford seems primed to receive more snaps with the first-team defense.