Krishna becomes our internal spiritual master through the external spiritual master

Krishna does not become the direct spiritual master unless one is fully trained by His representative spiritual master. Therefore,…the Lord’s representative spiritual master should not be considered an ordinary human being. The representative spiritual master never gives any false knowledge to his disciple, but only perfect knowledge. Thus he is the representative of Krishna. Krishna helps as the guru, or spiritual master, from within and from without. From without He helps the devotee as His representative, and from within He talks personally with the pure devotee and gives him instructions by which he may return home, back to Godhead.

Srimad Bhagavatam 7.15.76 purport