This could be interesting. While I think Mirabelli is a good catcher who can handle the starting catchers role, picking up Lopez would be a great move for the Red Sox. He's certainly better than any other option they have in house.
BostonHerald.com - Boston Red Sox: Varitek keeps positive outlook
The Sox are believed to be exploring a deal for Baltimore’s Javy Lopez, a poor defensive catcher who could clear waivers as soon as today. Another option would be to pursue a more defensively skilled catcher to work in a rotation with Mirabelli and, perhaps, Ken Huckaby.
Hopefully, the Sox take care of business over the next 10 days or so given what their opponents are going to look like after that. (Starting on August 14th, the Red Sox will be facing Detroit, NY, LA, Seattle, Oakland, Toronto and the White Sox). Hopefully they'll make a quick move to cover the catchers role so Lopez (or whoever) can get acquainted with the pitchers before those series begin.