BALTIMORE -- The Orioles will balance need against a reward for a job well done when Major League rosters are expanded beyond the normal 25-man limit on Tuesday. Manager Dave Trembley is being mum about exactly what players will join the team, but he's emphatic about who's not being summoned from the Minor Leagues.

Who's out? Pitching prospect Jake Arrieta and first baseman Brandon Snyder, two players who may figure prominently in the Orioles' future, won't have their seasons extended at Camden Yards. Who's in? Some additional relief help, maybe a starter, a third catcher and backups to bolster the infield and outfield.

"Arrieta's not coming. Snyder's not coming. That's not going to happen. ... Snyder's going to the [Arizona] Fall League, Arrieta's not coming," said Trembley, explaining that he'd discussed the subject with Orioles president of baseball operations Andy MacPhail and that MacPhail and he were on the same page.

Instead of adding to the already impressive collection of young players that form the nucleus for the future, the Orioles will try to add in-game flexibility by increasing the size of their bench.

The arrival of a third catcher -- either Robby Hammock or Guillermo Rodriguez could get the call from Triple-A Norfolk -- would give Trembley the ability to use rookie backstop Matt Wieters as a designated hitter on days he's not catching without worrying about breaking the DH if he needs to pinch-hit or pinch-run for Chad Moeller late in a game.

"I think we need a third catcher," Trembley said. "At the same time, you're rewarding somebody you think has done a nice job, would fit in here and knows his place."

Hammock is hitting .198 with four homers and 23 RBIs at Norfolk, while Rodriguez has a .249 batting mark with five homers and 26 RBIs in 83 games between Norfolk and Double-A Bowie.

Infielder Justin Turner could get the call to spell Brian Roberts at second base, Cesar Izturis at shortstop or Melvin Mora at third base. Turner, acquired from Cincinnati in the trade that sent catcher Ramon Hernandez to the Reds in the offseason, was a pleasant surprise in Spring Training, when he hit .295 with three homers and 10 RBIs. At Norfolk this summer, Turner is hitting .303 with two home runs and 42 RBIs in 105 games, mostly at second base.

"There are times I want to get Mora or Izturis out of the game," Trembley explained. "At the same time, it's someone you might want to look at who fits into your plans in the future."

Likewise, the arrival of another outfielder could allow Trembley to give one of his regulars a blow or provide a pinch-running option late in the game. The most attractive options at Triple-A may be Jeff Fiorentino (.306, 12 homers, 64 RBIs). Joey Gathright was considered a candidate for promotion before he was traded from Norfolk to Triple-A Pawtucket on Saturday.

Trembley expects to get some bullpen reinforcements, but the club may also pluck another starter from the Minors. With disabled right-hander Brad Bergesen's bruised left shin slow to heal, the Orioles manager may need another starting pitcher to fill out the six-man September rotation he wants to use to limit the number of innings thrown by the team's young pitchers. That could create a need for right-hander Chris Lambert, who was acquired off waivers from Detroit and is 6-9 with a 3.85 ERA in 23 starts for Triple-A Toledo and Norfolk in 2009. Either way, there will be an additional need for relievers, too.

Right-handers Dennis Sarfate, who has been working back from circulatory problems and remains on the 15-day disabled list, and Koji Uehara, currently at the Minor League facility rehabilitating a right elbow injury, could be added to bolster the bullpen. Other potential relief candidates at Norfolk include right-handers Jim Miller (16 saves, 2.80 ERA), Matt Albers (1-0, 5.68 ERA) and Bob McCrory (0-2, 3.99 ERA), or left-handers Alberto Castillo (13 saves, 2.77 ERA) and Chris Waters (9-5, 4.19 ERA).

To accommodate any additions to the 40-man roster, the Orioles will have to do some maneuvering. Baltimore could move any of several injured players on the 15-day disabled list -- including Bergesen, left-hander Rich Hill or outfielder Lou Montanez -- to the 60-day disabled list to open a spot on the 40-man. Neither Hammock, Rodriguez, Turner nor Fiorentino currently are on the 40-man roster and would have to be added.

Trembley expects the roster additions to come in two waves. The first few players will arrive when rosters expand Tuesday, with other reinforcements following once the Minor League season ends Sept. 7.