Under O’Reilly’s steady direction, Philadelphia can sometimes feel like the dramatic equivalent of “old Screwballs” — it’s straightforward and decent and, theatrically, not given to unpredictability. Still, some of the production’s strongest moments are the play’s sketches of its menfolk. It’s in these scenes where Friel’s observational powers most fully emerge, his deftness with people who live right on the edge of caricature and yet, in startling lucid glimpses, can sense their own absurdity and helplessness.