Isn't there an opinion in the Talmud that there will be no redeemer except for G-d Himself?
The Talmud decisively rejects this opinion, and rules that The Redemption will come about through a human being
Belief in Moshiach is one of the thirteen principles of faith codified by Maimonides: "I believe with perfect faith in the coming of the Moshiach. Even if he may tarry, I wait for him every day to come." In other words, we believe that a human being will arise who will redeem the Jewish people from exile and lead them to the ultimate Redemption.
The Talmud does express an alternate view, expressed by Rabbi Hillel, who said: "There is no Moshiach in Israel", "G-d alone will be sovereign over them and will redeem them." However, the Talmud decisively rejects this opinion, and rules: "The Redemption will come about through a human being, as specified in the prophecy of Zechariah: "Behold, your king who is coming to you is righteous, and he will save you." The Talmud then says in relation to Rabbi Hillel, that G-d will forgive him for his statement.
The Chasam Sofer adds that one who holds like Rabbi Hillel and believes that there will be no redeemer is denying the entire Torah. Since the majority of Rabbis held that there will be a human redeemer, their view is the deciding one according to the rules of the Torah. Thus, continuing to maintain an alternate view is to reject the principle of majority rule laid down by the Torah itself. The final halacha of the Talmud is that a king from the House of David will arise and redeem the Jewish people from exile.
(Dvar Malchus 12, Chapter 2)