Castro is not in Friday's lineup against the Cardinals due to plantar fasciitis, Kevin Henry of The Denver Gazette reports.
It's not clear when the injury flared up for Castro. He's being evaluated by medical staff, and the Rockies should have an update on the 29-year-old utility man over the coming days. He is slashing .260/.331/.417 with 10 steals, 15 home runs and 56 RBI over 477 plate appearances this season.