The Brazilian right-back, 22, wants payback over rivals City for nicking the title on goal difference last season.
Rafael said: "There is definitely a determination to get the title back after the way we lost it. It was hard to take.
"We will never forget how we felt after the last game. We just looked at each other and asked, 'How did we lose that?' After last season, we just want the title back."
City slipped three points behind United last weekend and Rafael added: "To get a six-point lead over them is very important.
"If we open the gap it can make the other team nervous and make it easier for us."