The Phillies have one of the best first base prospects in all of baseball in Rhys Hoskins who has been an above-average hitter in Triple-A this year. Through 112 games he has a .280/.385/.570 line with 27 home runs and 84 runs batted in. Most teams would have promoted him long ago.
However, the team is caught in a jam because they already have a right-handed hitting first baseman in the majors in Tommy Joseph. He is the reason why Hoskins hasn’t been promoted yet, although I’ve written before about why this logic was off.