Everyone assumed that Brandon Lyon was blowing saves by the carton because he was Brandon Lyon -- competent and perfectly decent middle reliever, but no one's idea of a dominant closer. Turns out, though, there might be something more sinister at work. From Alyson Footer:

Brandon Lyon is flying to Houston today to be looked at by Dr. Lintner for shoulder weakness.

Lyon's blown save on Wednesday was his fourth of the 2011 season, the same number that cost Ryan Franklin and Jonathan Broxton their jobs. Per the PITCH f/x numbers at FanGraphs, Lyon's velocity has been noticeably down this year, and a fatigued shoulder -- or worse -- would go a long way towards explaining his ineffectiveness. Lyon has thrown 11-1/3 innings this season, giving up 21 hits and three walks and striking out five.

The Astros don't have an obvious candidate to replace Lyon in the closer's role, though Rotoworld is speculating that Mark Melancon might be the pitcher who has first dibs at filling in.