In another move, San Diego outrighted catcher Kyle Phillips to Tucson. Phillips, 27, was designated for assignment on Aug. 31.
Carpenter, 26, has gone 0-0 with a 7.71 ERA and 10 strikeouts against four walks over six appearances for Philadelphia.
Martinez, 26, is starting his third stint with the Padres this season. The rookie was previously optioned to Tucson on Aug. 12.