Service to ones Acharya is superior to serving God Himself. And this is demonstrated in Sabari moksha, said Akkarakkani Srinidhi, in a discourse. Sabari had served Matanga maharishi with great devotion. Moksha, therefore, was guaranteed to her. She stayed on in the ashrama, knowing Rama would arrive, and she welcomed Him with offerings of fruits, which Rama gladly accepted, because He was pleased with her Acharya bhakti. When Sabari departed from the earth, she asked Rama to be witness to her departure. So, it was her devotion and service to her Acharya, sage Matanga, which earned moksha for her. Vedanta Desika observed that what an Acharya confers with his two eyes, what even three eyes, eight eyes or a thousand eyes cannot do. The usual interpretation is that Siva, the three eyed deity and Brahma is the eight eyed one, and Indra is the thousand eyed one.
But scholar Prativadhi Bhayankaram Annangarachariar came up with a unique interpretation of Desikas verse. He said that having mentioned Brahma and Siva, there would be no point in mentioning Indra, who was lower down in the hierarchy than Siva and Brahma. So, the thousand eyes must be a reference to Vishnu. What Desika is saying is that even Siva, Brahma and Vishnu cannot do for us, what an Acharya can do. Such is the greatness of an Acharya. Vaishnavite Acharya Thirukkoshtiyur Nambi said that an Acharya imparts a glow to his disciple, so that when the jivatma reaches Sri Vaikuntha, it shines like Sri Devi Herself!
When Ramanujacharya went to Thirukkurungudi, the deity of the temple there marvelled at people paying attention to Ramanuja, while they had not paid heed to the Lord Himself. So, He asked Ramanuja to be His teacher. Because of this, the deity came to be called Vaishnava Nambi.