There are plenty of candidates. With Brad Lidge out three to six weeks with what's being termed a shoulder sprain, Mike Stutes is now a candidate for a spot on the bullpen roster. The 24 year old right-hander has been impressive in the minors as he's worked his way through the system and has also turned in an eye opening performance this spring, despite being moved to minor league camp fairly on. That seeming demotion may turn out to be a blessing in disguise for Stutes, who went to minor league camp without a complaint and pitched well there. The Phillies have summoned him back to the big league camp on a couple of occasions and he has continued to pitch well during those opportunities as well.
With the second base and utility infielder spots being up in the air right now, it's unclear if the Phillies will need a spot - or possibly two - on the 40-man roster. Wilson Valdez has made the club and is on the 40-man roster. Michael Martinez, a Rule 5 Draft pick, is on the 40-man, but has not cemented a spot with the big league club. If he's offered back to the Nationals, they will likely welcome him back, which would open up another spot on the roster, but the Phillies would like to keep him in the organization, if at all possible.
The other candidates - Luis Castillo, Pete Orr and Delwyn Young - are all in camp on minor league deals. It's not out of the question that two of them could make the club and would need roster spots to fill. Odds are that only one of them will get a big league job in Philly.
As for opening other roster spots, both pitcher Brian Schlitter and infielder Brian Bocock are out with injuries and could possibly wind up on the 60 day DL, which would allow the Phillies to remove them from the 40 man roster. Pitcher J.C. Ramirez has been shaky in camp and could possibly be dropped from the roster.