Castillo signed a minor-league contract with the Twins on Wednesday.

Castillo elected to become a free agent after he was pushed off the Twins' 40-man roster in June, and he will now return to the organization after exploring his options in the open market. The 30-year-old right-hander will report to Triple-A St. Paul, where he's put up a 2.50 ERA and 1.06 WHIP over 18 innings this season.