Who was the Buddha's teacher?

When Asita muni had told to King Shuddhodhana that >" If he becomes a householder, he will become a universal monarch. But if he goes forth from the home to a homeless life, he will become a fully enlightened Buddha." Asita was sure that the child would not remain a householder. So when Asita was known all that, may we suppose him Buddha's teacher and if wasn't then who was Buddha's teacher.