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Ahead of their clash with the Red Sox that begins Friday night in Houston, the Astros have announced their roster for the ALCS. Most notably, ace Lance McCullers Jr. was left off. McCullers exited his ALDS Game 4 start against the White Sox with forearm discomfort, and the Astros have presumably reached the conclusion that he'll be unavailable to pitch against Boston. Replacing McCullers on the roster is right-hander Jake Odorizzi

This is indeed a serious blow to Houston. The 28-year-old McCullers during the regular season pitched to a 3.16 ERA/136 ERA+ with a 2.43 K/BB ratio across 28 starts and 162 1/3 innings. He led all Houston pitchers this season with a WAR of 3.5. In two starts against the White Sox in the ALDS, McCullers allowed only one run in 10 2/3 innings. 

Manager Dusty Baker has opted to start Framber Valdez in Friday's series opener and then Luis Garcia in Saturday's Game 2. Beyond that, though, things are uncertain. José Urquidy figures to draw a start, since he was in line to start ALDS Game 4 against Chicago before a rain-out pushed the game back a day and allowed McCullers to take the bump. As for the fourth starter in the series, Odorizzi is an option, or Baker could go with a bullpen game. Giving a start to Zack Greinke seems unlikely as he figures to remain in the bullpen. 

Elsewhere on the Houston ALCS roster, third catcher Garrett Stubbs has been left off, and lefty reliever Blake Taylor has been added.

Even with the loss of McCullers, however, one can argue the Astros still have a better current rotation than the Red Sox. Nathan Eovaldi is a worthy ALCS starter for Boston, but given the post-Tommy John struggles of Chris Sale they're light on known quantities elsewhere in the rotation. 

The Astros haven't provided any details about McCullers' injury, so at this time it seems at least theoretically possible that he could return in time for the World Series should they advance.