The Twins selected Castillo's contract from Triple-A St. Paul on Sunday. He'll start at third base and bat seventh in the Twins' series finale in San Francisco.
Castillo joined the Twins' 26-man active roster as replacement for infielder Jose Miranda, who was placed on the 10-day injured list with a low back strain. Over his 283 plate appearances with St. Paul this season, Castillo slashed a respectable .269/.375/.399 with five home runs and seven stolen bases while seeing action at all four infield spots as well as in right field. He'll likely see most of his starts against left-handed pitchers like the Giants' Blake Snell while he's up with the big club.