The centre-half arrived in January on loan from Schalke as Jurgen Klopp battled an injury crisis at the back.
Kabak was a regular in defence during his short stint at Anfield, but on Monday he moved out of his house in Formby ahead of his return to Germany.
Liverpool could've retained his services by triggering an £18m option in his loan deal, but opted not to.
He said: "Ozan was absolutely incredible, he did a great job and not to forget he is a young, young, young boy with incredible experience already.
"He was in different clubs, moved early from Turkey to Germany. Played in two big clubs in Germany in difficult situations, which is obviously not his fault.
"We could all see when he arrived here he needed a little bit of time to adapt. Then he played super games for us; I don't want to pick any games out, but the two Leipzig games were absolutely incredible if you think how good Leipzig can be."