The South American pair have been excellent in tandem recently and are building an understanding that may one day rival that of Gary Neville and David Beckham.
"To be honest, I think it's well recognised by everybody that Antonio has been one of my best friends at the club," Rafael told MUTV. "That's not to disrespect anyone but I think we have created a very good understanding on the pitch.
"I can feel what he wants to do and vice versa and that is probably the reason why we have so much understanding on the pitch.
"I think it's quite difficult to define Antonio's qualities on the pitch. He's quite fast and direct. He looks for the ball all the time. If I go forward, he covers me at the back and vice versa. It's easy to work with him and, when I see him on the pitch, it leaves me more relaxed due to the understanding we have on the field."