I'm not wild about Garcia, and the Sox have had plenty of good defensive RFers even before Betts, including JD Drew, Trot Nixon, and Shane Victorino. During the years the Sox used lesser defensive right fielders like Billy Hatcher, Darren Bragg and Cody Ross, the team was usually not very good.
I don't think they leave RF up for anyone with a bat. At least I hope not...