The Mets released Smith on Monday, Michael Mayer of MetsmerizedOnline.com reports.
The Mets signed Smith to a minor-league contract Sunday with an invitation to major-league spring training, the Associated Press reports.
The Athletics outrighted Smith to Triple-A Las Vegas on Monday.
Triple-A Las Vegas placed Smith on its 7-day injured list Aug. 12 with an unspecified injury.
Smith was optioned to Triple-A Las Vegas on Tuesday.
Smith (1-2) took the loss against the Astros on Sunday, allowing an earned run on a solo home run over 1.2 innings. He also issued a walk and hit a batter.
Smith's contract was selected by the Athletics on Saturday.
Smith cleared waivers and was outrighted to Triple-A Las Vegas on Thursday.
Smith was designated for assignment by the Athletics on Tuesday.
Smith was optioned to Triple-A Las Vegas by the Athletics on Tuesday, Martin Gallegos of MLB.com reports.