The guys who are eligible for rule 5 if they're not added are:
Michael Almanzar, Chris Balcom-Miller, Luis Bastardo, Jeremiah Bayer, Ronald Bermudez, Carson Blair, Dan Butler, Miguel Celestino, William Cuevas, Jose De La Torre, Ryan Dent, Marco Duarte, Leonel Escobar, Josh Fields, Jose Garcia, Zach Gentile, Derrik Gibson, Aly Gonzalez, Alex Hassan, Jeremy Hazelbaker, Drew Hedman, Jon Hee, Pete Hissey, Brock Huntzinger, Jeremy Kehrt, Will Latimer, Mitch Maier, Heiker Meneses, Boss Moanaroa, Gerardo Olivares, Oscar Perez, Ryan Pressly, Manny Rivera, Charle Rosario, Pete Ruiz, Felix Sanchez, Matt Spring, Kyle Stroup, Tony Thomas, Christian Vazquez, Raynel Velette, Allen Webster, Ryan Westmoreland, Shannon Wilkerson, Tyler Wilson, Alex Wilson, and Steven Wright.
I could see the Sox trying to protect Balcom-Miller, Allen Webster, Dan Butler, Josh Fields, Christian Vazquez, Jeremy Hazelbaker, Alex Wilson or Steven Wright. The Boston Red Sox currently have 39 spots taken on the 40 man roster. Mike Andrews thinks the primary candidates to be added to the 40 man roster are Webster, Vazquez and Alex Wilson.