Romero will open the season at Double-A Reading, MLB.com's Jonathan Mayo reports.
Romero has made a swift ascension through the Phillies' system, opening at Low-A last year and earning a midseason promotion to High-A. He has never logged an ERA above 2.56 in the minors, but projects to be more of a No. 3 or No. 4 starter long term. Romero is not on the 40-man roster, so he may not make a fantasy impact until 2019.