Here [John 15:1a] we have a case where both “I” (ἐγώ) and “my father” (ὁ πατήρ μου) have been fronted. Now I can imagine a preacher with a couple years of Greek under his belt explain to a congregation that because these two entities are placed before the verb at the beginning of the sentence that Jesus is stressing the fact that it is he who is the true vine and no one else, that it is his father that is the vinedresser and no one else. And maybe he got this from a commentary!
The sad part is—and let this be a cautionary tale to all my readers—that because the preacher referenced the Greek language, the congregation is probably giving him some mad props and thinking that somehow he figured something out the typical lay could not—while the truth is simply that this line of interpretation just isn’t the case. Even though it could make sense, it doesn’t make it an accurate route of exegesis.