The Pittsburgh Pirates‘ difficult start to the 2013 season encountered another obstacle Monday night, as starting pitcher Wandy Rodriguez left the Bucs’ 5-3 victory in the third inning with a tight left hamstring.

Rodriguez was expected to be re-evaluated on Tuesday, and the extent of the injury is at this point unclear. But if Rodriguez is sidelined for an extended period of time, the Pirates’ suddenly thin rotation will face a big challenge.

The Pirates’ rotation features several hit or miss players, with Rodriguez perhaps representing the safest option Clint Hurdle has at his disposal. Though A.J. Burnett, the Bucs’ clear ace at this point, put together a rather consistent year in 2012, he does not have a track record anywhere close to Wandy‘s in this department.

The current Pittsburgh rotation also features James McDonald and Jonathan Sanchez, two pitchers who are capable of excellence or incompetence on any given day. Rodriguez is an important stabilizing force for this ballclub.

Tim Williams posted a good breakdown of Rodriguez’s potential replacements this morning, and though the options look decent at first glance they underscore the fact that the Bucs are not prepared for this injury.

Kyle McPherson and Phil Irwin, the two most likely fill-ins, both may very well be deserving of Major League jobs, and each will likely make it to Pittsburgh at some point this season. But the Pirates’ brass did not believe either pitcher was a better short-term option than Jonathan Sanchez a week ago, which is rather disconcerting.

The organizational view is clearly that McPherson, who struggled towards the back end of Spring Training, and Irwin both would benefit from more time in Triple-A. For this reason it may be more likely that Irwin, who is slightly more “Major League-ready” but has a lower ceiling, gets the first call-up.

Neither option is a total disaster for the Bucs, but the Pittsburgh rotation was already in a pretty tenuous position to begin with. The Pirates’ offense may find the need to break out of its early-season doldrums even more urgent soon.

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