Even though he is arguably the most talented prospect in all of baseball, don't expect Matt Wieters to blossom into a superstar from the get go.
If history is any indication, it is unlikely that Wieters will be an impact player in his first couple months with the O's. While anyone is an upgrade over Gregg Zaun and Chad Moeller, don't expect Wieters to instantly provide a solid bat in the middle portion of the lineup.
Even the most highly rated prospects struggled in their first couple months in the big leagues. Nick Markakis, for example, batted .220 in his first 100 at-bats with only 2 homers. Through their first 100 at-bats, Adam Jones (.210), Evan Longoria (.220), and Dustin Pedroia (.180) each struggled in the first couple of months after getting called up. However, after their initial struggles, all of the aforementioned players turned into impact players.
Rarely will a rookie will burst onto the scene in the couple months following their call-up. Joe Mauer is an example of such a rarity. The batting title-winning Mauer hit .320 to go along with 6 HR's in his first 100 AB's.
As for Wieters, he may join the likes of Joe Mauer and immediately live up to the hype. Prior to the 2009 season, a large handful of 'experts' including ESPN's Buster Olney picked Wieters to win the AL Rookie of the Year award. Olney believes that Wieters is 'Joe Mauer, with power.' It is possible that Wieters comes right out of the gate swinging. However, a player like Mauer is an anomaly. While some have considered Wieters to be an anomaly as well, I am not going to be foolish enough to expect too much out of this kid before he settles into the major league environment.
Either way, the Orioles don't need him to produce in the short run. If Wieters is batting under .230 halfway through July, don't panic. This kid seems like the real deal but we have to give him time to develop, much like the Orioles team as a whole.