Contreras (knee) reported to Triple-A Iowa to begin a rehab assignment Tuesday.
Contreras progressed to catching bullpen sessions and taking part in baserunning drills over the weekend, which were apparently some of the final hurdles before starting a rehab stint. The 29-year-old has been sidelined nearly three weeks by the knee sprain, and he should be able to rejoin the big-league club after a few appearances in the minors.