We know that Greek dialect and alphabet had some influence towards the development of Latin speech and writing, however should we take into account that then again Latin could also have a reverse effect into native Greek tongue as well? Since Rome eventually dominated the Mediterranean, especially Greece, Latin became the dominant language. I can think of some examples where Latin had an influence into native dialect; the Germanics and the Britons were a couple examples.

This diffusion was not forced; they blended naturally from casual conversation. Brining up names, places, new terms and such will eventually have an impact on native speech. The dominance of Rome had to have slightly changed Greek dialect in some way; especially during the Christianization of the Roman empire when missionaries preached their work in Latin.

Though, as I type I can think of a couple examples that can prove that this never happened. The first being Rome's preservation of Greek culture. The other being the fact that the east remained a primarily Greek speaking region, especially at the development of the Byzantine empire. The Pelopponese may have been too rural for such diffusion to take place.