Matthews (undisclosed) was placed on the Double-A Corpus Christi's 7-day injured list Sunday, Chandler Rome of The Athletic reports.
Matthews last saw the field Aug. 4, and it's unclear how long he's expected to be sidelined. The 22-year-old has produced a .234 average with six home runs, 13 RBI, 19 runs scored and 10 stolen bases over 111 at-bats in 30 games with Corpus Christi this season.