I*n Evangelical circles, the “little rock, big rock” theory is fairly recent. Nearly every Protestant commentary written in the last 50 years interprets Peter as the rock upon which the Church was built. (However, they didn’t believe that Peter had a successor, more about that here ). The scholarly Evangelical work, Carson’s “Expositors Bible Commentary” explains this well. It is in the section on Matthew 16. These Evangelical scholars looked closely at the Greek word for rock “Petra” and determined that it refers to Peter. The early Christians also referred to Peter as the Rock. Some Quotes are here.
I don’t think the “little rock, big rock” theory hold up under scrutiny. I think Jesus built his Church on people, not a declaration. Following through on the passage we see that Jesus gave the keys to the kingdom to St. Peter, not to his declaration. The Reformer, Martin Luther, said this:
Why are you searching heavenward in search of my keys? Do you not understand, Jesus said, 'I gave them to Peter. They are indeed the keys of heaven, but they are not found in heaven for I left them on earth. Peter’s mouth is my mouth, his tongue is my key case, his keys are my keys. They are an office. They are a power, a command given by God through Christ to all of Christendom for the retaining and remitting of the sins of men. (Martin Luther 1530 - after he left the Church)(1)
W. F. Albright, one of the best known Protestant theologians of this century, in his Anchor Bible Commentary, says:
Peter as the Rock will be the foundation of the future community, the church…To deny the pre-eminent position of Peter among the disciples or in the early Christian community is a denial of the evidence.
I recently spoke with a grammar specialist who is not Catholic. She explained to me that the adjective “this” grammatically must refer to the nearest preceding noun, which was Peter, not his declaration which occurs two verses earlier. *