The Red Sox reassigned Guthrie to minor-league camp Monday.
Guthrie signed a minor-league contract with the Red Sox on Tuesday.
Guthrie cleared waivers and was outrighted to Triple-A Gwinnett on Sunday, Justin Toscano of The Atlanta Journal-Constitution reports.
Guthrie was designated for assignment Friday.
Atlanta claimed Guthrie off waivers from the Giants on Thursday and optioned him to Triple-A Gwinnett.
Guthrie was designated for assignment by the Giants on Thursday.
Guthrie was traded from the Phillies to the Giants in exchange for cash considerations Thursday.
The Phillies designated Guthrie for assignment Monday, Corey Seidman of NBC Sports Philadelphia reports.
The Phillies optioned Guthrie to Triple-A Lehigh Valley on Friday.
Guthrie is out of the lineup for Wednesday's game against the Diamondbacks.