The fighter. The lover. The friend. Just don't think that 9 is the fighter, 10 is the lover, and 11 is the friend. In every regeneration each one is all these things. Remember, they are all the same man.
I love how having a small role on Doctor Who doesn't prevent you from getting a larger one later. Oh and don't forget, that Roman father guy in that Pompeii episode what was his name was played by Peter Capaldi, later to become the Twelfth Doctor