I think Houston is a larger market than Boston.
Houston is about 2.5 million people.
Red Sox nation is most of New England except for SW CT.
All of NH, ME, VT, RI, MA and half of CT(10 million).
Not to mention all the Sox fans around the country outside of NE.
I think only the Yankees have more MLB fans.
The Rays and Oriels management love it when the Yankees and Sox come to town. Their stadiums actually fill up with fans.