Holderman was optioned to Triple-A Indianapolis on Saturday, Mike Persak of the Pittsburgh Post-Gazette reports.
Holderman was traded from the Mets to the Pirates on Friday, and he'll be sent to the minors a day later. The right-hander made five major-league appearances between the two teams in July and allowed a run (zero earned) on a hit and three walks while striking out four in 6.1 innings.