Though I have followed a grammar-based approach for Marathi teaching; I have purposely omitted explaining the concept of विभक्ति(vibhakti) and विभक्तिप्रत्यय(vibhaktipratyay).
I think it is very complicated to explain and a lot confusing. Because “विभक्तिप्रत्यय” table includes many suffixes which are not used in contemporary language.
I had read in one place that in modern languages there is less number of cases. And cases were replaced by prepositions in the evolution of languages. e.g. in Sanskrit and in Marathi, there are 7 cases; in German, there are 4 cases while in English there are only 2 cases.
I decided to teach Marathi in terms of English i.e. prepositions
e.g. “second vibhakti” is actually preposition “To”
The third vibhakti is preposition “by” as used in past tense. etc.
For more grammatical details of विभक्ति(vibhakti) refer to section “Nominal inflection” section of Wikipedia link