BALTIMORE -- Everyone knows Matt Wieters is coming Friday and that he'll basically assume the starting catching job once he arrives. The Orioles still aren't sure how it will affect their roster in one respect, though, with the team deliberating whether to keep Gregg Zaun or Chad Moeller as their backup backstop.

Zaun, who was signed during the offseason to be the starter until Wieters arrives, has batted .214 with a .323 on-base percentage in the season's first seven weeks. A few pitchers have expressed a preference for throwing to Moeller over Zaun, opening up the possibility for a roster-related upset.

Moeller is hitting just .200 in 50 at-bats entering Thursday, but the Orioles feel that both he and Zaun could provide a suitable mentor to their prized young prospect. Now, it's just deciding who's a better fit. Both Moeller and Zaun signed one-year contracts with options for 2010, giving the Orioles security in whomever they keep.

"I'm very fortunate that we've had guys here of experience, but the unpleasantness of having to tell somebody they're going to get sent down is not easy to do," said manager Dave Trembley. "If you tell somebody up here they're going from the big leagues back to the Minor Leagues, that's probably one of the more challenging things you're faced with doing as a manager. ... But also, it hasn't been a secret that Matt Wieters was going to come.

"We knew that going in, and the guys that are in the position they're in knew that as well. You still have to be respectful, compassionate and understanding of their their particular place in time."