Holderman was traded to the Pirates in exchange for Daniel Vogelbach on Friday, Evan Webeck of The San Jose Mercury News reports.
Holderman will head to Pittsburgh after producing a 2.04 ERA and 1.02 WHIP with 18 punchouts over 17.2 innings in 15 appearances with the Mets this season. He'll likely fill a middle relief role with the Pirates, but the rookie could slip into a high-leverage spot if the Bucs trade some veteran relievers at the deadline.