The Twins optioned Matthews to Triple-A St. Paul on Saturday, Dan Hayes of The Athletic reports.
After striking out 10 batters in five innings during his start Friday, Matthews will head back to the minors to create roster space for A.J. Minter and open a spot in the rotation that will presumably be filled by Dean Kremer. Matthews has posted a 5.22 ERA and 1.52 WHIP in 81 innings this season and is likely to remain as a depth piece at St. Paul for most of the remainder of the year, barring an injury to one of the Twins' starters.