With a scheduled off-day today, the Baltimore Orioles get a full 48 hours in which to revel in their surprising 4-0 start, which included a resounding 5-1 win over the Detroit Tigers in the Orioles’ home opener Monday in front of a full house at Oriole Park at Camden Yards.

What’s more impressive about the Orioles’ start? The fact that their starting rotation has a 0.69 ERA? The fact that their defense has committed only one error? Or the fact that the rebuilt heart of their lineup hasn’t even produced much offense yet?

Far be it for me to start looking for flaws in the Orioles, or to deny long-suffering Orioles fans their first glimpse of precious hope in years. But there’s one major reason why I find it difficult to imagine the Orioles maintaining this level of play: a lack of organizational depth, particularly in starting pitching.

Already, the Orioles have found themselves without two projected members of their starting rotation, veteran right-hander Justin Duchscherer (hip) and young lefty Brian Matusz (back). Now comes word that a third starter, right-hander Jeremy Guthrie, is sidelined with pneumonia.

For now, the Orioles are managing just fine. Chris Tillman, essentially filling Duchscherer’s spot, no-hit the Tampa Bay Rays for six innings on Saturday before being pulled. Rookie lefty Zach Britton filled in for Matusz on Sunday and delivered a six-inning gem to beat the Tampa Bay Rays. Brad Bergesen, the long man in the bullpen, will assume Guthrie’s spot on Wednesday.

But things are already getting tricky for the Orioles.

Given Duchscherer’s checkered injury history and a troublesome hip problem, the Orioles have no idea when, or if, he will pitch for them this season. If Guthrie is forced to miss another start beyond Wednesday’s, the Orioles may be forced to dip into their pool of inventory at Class AAA Norfolk – perhaps former Washington National Ryan Drese, one of the last pitchers the Orioles cut this spring.

And in an ideal world, the Orioles would prefer for Tillman and/or Britton to pitch at Norfolk before coming to the big leagues to stay. That may no longer be an option.

It’s well understood in baseball that a team needs at least seven or eight dependable starting pitchers over the course of a season, given the rate of attrition for pitchers. (The 2010 San Francisco Giants, whose entire rotation stayed healthy for an entire season, was an aberration.) Meantime, the Orioles’ pool of fill-ins at Norfolk – essentially their sixth, seventh and eighth starting pitchers -- includes such notables as Drese, Chris Jasubauskas and Michael Ballard.

Maybe the Orioles will get lucky. Maybe Duchscherer will return to health and give them 25 starts. Maybe Matusz will make a quick return and take the ball 30 times. But right now, as amazing as their start has been, the Orioles don’t have the depth to absorb any more injuries to their pitching staff.