Martes was designated for assignment by the Astros on Wednesday, Brian McTaggart of MLB.com reports.
The 25-year-old spent the first couple months of the season on the restricted list while serving a PED suspension, and he's now lost his 40-man roster spot. Martes has made seven appearances at Triple-A Sugar Land and surrendered 10 runs on eight hits with 13 walks and nine strikeouts over 8.1 innings.