Manager Rob Thomson said Friday that he expects Robertson to join the active roster Sunday, Charlotte Varnes of The Athletic reports.
Robertson reported to Triple-A Lehigh Valley after signing a one-year deal with the Phillies on July 21. He's had mixed results with the IronPigs, surrendering three runs in one inning during two of his six minor-league outings while going without an earned run allowed during his other four. Despite his inconsistent performance, the 40-year-old veteran will nab a spot in Philadelphia's bullpen and is likely ticketed for a middle-relief role.