It is well known that some fourth-century members of the Church applied John 14:28 to the preexistent Son of God: B.F. Westcott painstakingly supplies details respecting the verse's history of interpretation. However, as one traces Dogmengeschichte from Athanasius of Alexandria onwards, one finds that the post-Nicenes eventually applied John 14:28 to the enfleshed Son since talk of the preexistent Son's inferiority or lesser dignity made them uncomfortable. As Maurice Wiles relates, texts such as John 14:28 are applied to the Son qua the incarnate one and not to the second Person of the Trinity properly speaking. Below are some notes from my thesis on Tertullian. At the time I wrote them, I had not actually incorporated the notes into the final chapter of my M.Th. thesis; this material is taken from C.K. Barrett's Essays on John, page 27.
While some church fathers prefer to interpret John 14:28 as a reference to the human nature of Christ, Barrett contends that this understanding is neither the earliest interpretation nor the predominant one of the time. Yet both the Tome of Leo (Ad Flavianum, Epistola 4) and Augustine’s Tractate on John 78.2 apply John 14:28 to the human ousia of Christ. On the other hand, most pre-Nicene writers think that Jesus' words are to be explained "independently of the circumstances of the incarnation." Barrett lists Tertullian's Adversus Praxean 9 as one example of this understanding (i.e., the text is applied to the preexistent Son of God). Another is Adversus Praxean 14, and in Adversus Praxean 22, Tertullian also refers John 10:30 to the heavenly Logos (Barrett, 27).
Finally, Origen thinks John 14:28 teaches that the Father is greater than the Son according to "their proper being and intrinsic relationship" (28).