Velasquez will start one of the two games during Sunday's doubleheader after Friday's game was rained out, Jim Salisbury of NBC Sports Philadelphia reports.
With Jake Arrieta lined up to start Saturday, Velasquez's start will be pushed back two days as a result of Friday's postponement. It's unclear whether he'll start the first or second game Sunday. The starter for the other game in the doubleheader hasn't officially been named, but top pitching prospect Spencer Howard could line up to make his major-league debut.