Precursors to Sai Baba:

Marianne Warren says that there is a history of Muslims in India “accommodating” Hinduism within traditional Islamic belief and practice.
I do not feel comfortable with the term accommodating, since it implies not being fully “Islamic” in a way. These figures who saw their Islam as so spacious that it could include their Hindu neighbors, would see this as being true to the universal message of the Qur’an and the sunna of the Prophet. To say their was a “watered down” Islam does injustice to the openness inherent in Islam.
Regardless, Warren mentioned figures that predated Sai Baba, and shared a similar stance of regarding Islam and Hinduism as inseparable, though outwardly different.

The first figure she mentioned is Shekh Mahammad (the spelling that’s provided). He lived from 1560-1650 and practiced in the Qadiri lineage.
One aspect of his life which was exceptional was taking on Hindu murids.
One such Murid was said to have shouted:
“Let the dharma as preached by Shekh Mahammad live!”
As is deminstarted by his own writing, Shekh Mahammad was a Muslim who was deeply committed to a unitive spiritual vision, where Islam embraced all. God, according to Shekh Mahammad is beyond the petty differences that humans experience. Thus, he was comfortable using Hindu deities and terminology in his discourses, not unlike the way Muslims call Allah al-Rahman, al-Karim, al-Wadud etc. :

“Salute to Sri Ganesha. Allah is great and the only one. He is loved, constantly praised by men. He is God, Rahimana, who envelops the universe. He is the real one; with a thousand names he pervades the universe. Realize this, and give up clamouring [about the duality of God], serve the real Guru. Muslims call him the real Pir and Marathas call him sadguru, the enlightened guru. Open your eyes brother, the two are the same. In fifty-two languages they start bickering about Allah who is one. In their tongues they quarrel, arguing with each other. Recognice the belief in duality [of God] as the sing of heresy. They lose sight of God in their quarrel. The self knowing one will profit himself with the blessing of the pir. The Persian ask for ab (water), the Maratha asks for pani (water), without knowing that the meaning of the words is the same. Due, to ignorance, their misunderstanding [of the meaning of the word] leads to a quarrel. The thirsty Kannada [a person who speaks Kannada language] asks for nirkuda (water), the Musalman said, “What is he babbling about?” The interpreter (dubhasi) [lit. bilingual person] silenced them both by giving them nira (water). Thus the key was used to unlock [the true] meaning [of God] in fifty-two tongues. Once they realized this [key to] knowledge, the fallacy dissipates. They understood the oneness of God.”

Clearly God’s unity extends beyond the bounds of each religion, seeing all that point toward unity as Islam, much as Muslim philosophers and mystics embraced the Greek philosophers as within tawhid (unity of God). Here Shekh Mahammad is saying something quite starting for many. Not only is God one, and Muslims one, but Hindus are also within the embrace of God. To argue about language is to miss the point. All need the Divine, and to literally or figuratively start wars of language is ignorant.
Next I will write about another important precursor to Sai Baba, Shah Muni.