When the Houston Astros designated Joe Thatcher for assignment, they were left with only one lefty in the bullpen, Tony Sipp. Sipp does not have the same zip on his fastball that he did last year but has been pretty consistent this season. The Astros have other options at Triple-A in Kevin Chapman and Luis Cruz, but Cruz is viewed as a starter and Chapman struggles with command.
The Astros didn’t have an option ready in-house, so they sought out Oliver Perez, who cleared waivers, from the Arizona Diamondbacks.