Riddle was acquired by the Mets from the Reds on Sunday in exchange for cash considerations, Anthony DiComo of MLB.com reports.
Riddle accepted an outright assignment to Triple-A Louisville on Thursday, C. Trent Rosecrans of The Athletic reports.
The Reds designated Riddle for assignment Tuesday.
Riddle had his contract selected by the Reds on Tuesday.
Riddle is expected to report to Triple-A St. Paul this week after going unclaimed off waivers, Darren Wolfson of 5 Eyewitness News Saint Paul reports.
RIddle (COVID-19 protocols) was designated for assignment by the Twins on Friday, Aaron Gleeman of The Athletic reports.
Riddle was placed on the COVID-19 injured list Wednesday as the result of being identified as a close contact of an infected person, Dan Hayes of The Athletic reports.
Riddle was placed on the COVID-19 list, Dan Hayes of The Athletic reports.
Riddle's contract was selected by the Twins on Wednesday, Do-Hyoung Park of MLB.com reports.
Riddle was reassigned to minor-league camp Saturday.