The Astros signed Otto to a minor-league contract Thursday.
The Padres designated Otto (undisclosed) for assignment Sunday.
Triple-A El Paso placed Otto on its 7-day injured list Sunday with an unspecified injury.
The Padres sent Otto (shoulder) to the Arizona Complex League on Tuesday to begin a rehab assignment.
Otto (shoulder) had a setback early in spring camp and is expected to open the regular season on the injured list, per MLB.com.
The Padres claimed Otto off waivers from the Rangers on Thursday.
The Rangers designated Otto for assignment on Tuesday.
Otto was recalled from Triple-A Round Rock on Monday.
The Rangers optioned Otto to Triple-A Round Rock on Sunday.
The Rangers activated Otto (lat) from the 60-day injured list Friday.