Michu has scored three times against the Gunners already this season, and Cazorla is wary of the threat his friend will pose at the Liberty Stadium.
"We played together in the youth teams at Oviedo, we are great friends and I know him well," he told Arsenal Player. "I'm sure we'll be texting each other between now and the game.
"A lot of people were surprised at his impact [in England] but I wasn't, absolutely not. I think he's an incredible footballer and also one that's only improving.
"Every day he has more potential. I'm very happy for him because we're such good friends and, above all, because he's playing so well in a team like Swansea."