PHILADELPHIA After trading off three players, general manager Ruben Amaro Jr. and manager Charlie Manuel have all but announced that they're holding tryouts for 2013.

The most obvious example is in left field, where Domonic Brown has supplanted Juan Pierre.But while the game changes in front of them, the Phillies' bullpen remains mostly the same. Due to a run of injuries in the season's first month to Mike Stutes, David Herndon and Jose Contreras a crop of young relievers have had what has amounted to a season-long, major league tryout.Having been thrown into the proverbial fire simply because there weren't any other options, the young relief corps should benefit going forward into 2013."There's no substitute for this experience none," 26-year-old right-hander Michael Schwimer said. "You can work on pitches and tinker in mechanics at any level, even in A-ball, but when those hitters come in and face you, that's when you get your real answer. It's, 'OK, I can work with this, or this works, this doesn't.' This is the real test up here."Schwimer, Jeremy Horst, B.J. Rosenberg, Joe Savery and Jake Diekman have all gone from no or little major-league experience to getting vital time in the bigs. If the rest of the relievers had been healthy, most of them probably wouldn't have had that experience."They have the talent (and) this is how they get better," Manuel said of his young relief corps' learning on the job training. "There might be some growing pains."Every day is a learning experience for a guy like Schwimer. After going eight straight appearances without allowing a run, he hung a slider to Jason Heyward and watched the ball sail into the right field seats for a home run."To a lefty, you can't throw a get-me-over slider, where in a lower level they might take that because it's a breaking pitch. It's that kind of stuff you file away."The experience the young pitchers have gained this season should go a long way into the Phils management having a better idea of what they should have when spring training begins next season. Schwimer, for one, has grown in his three-plus months in the big leagues this season.Schwimer gave up at least one run in four of his first five outings this season; he had a 7.56 ERA with three strikeouts and six walks in his first nine games.But in his last 21 games, Schwimer has a 2.11 ERA, has held hitters to a .194 batting average and has racked up 25 strikeouts while talking nine in 21 innings."It's been great to be given that opportunity," Schwimer said. "I've been able to pitch in every situation imaginable, from tie games to getting one out, to late-inning situations … I've done it all. And I think that's really, really helped."