The question is not put correctly. Just think, if a savage Chief, say, the Bunga Gunga, which means, "Eagle's Soar", says to his tribe during a killing draught: "My brethren, I will ask our shamans to pray and the saving cloud will come and its raindrops and the wetness that will permeate the arid earth will give to our tribe salvation!" And now, some idle quibbler from the tribe who is especially fond of casuistics, whose name is Dakktaa Punkaa, which means, "A buzzing mosquito", asks: "So, after all, o, Chief, what is our savior, a cloud, raindrops, or humidity?" And the Eagle's Soar will punish the Buzzing Mosquito by calling him publicly "Kunga Munga", which means "Futile Questioner!" and the shame of this name spreads to seventeen generations in this tribe. Why futile? Because as the Eagle's Soar explained later, the cloud cannot save unless by the raindrops it sends and by the wetness those raindrops introduce in the arid soil.
The exact same in this passage! The Holy Spirit poured through and only through Christ on humans is a sine qua non for salvation, and so the Father cannot, totally, essentially, ontologically, achieve salvation of mankind, which He desires, unless through Christ and Holy Spirit, which fact necessarily makes both Christ and Holy Spirit ontologically necessary for God the Father, to the effect that since everything ontologically necessary to and indispensable for God is God, then with the Father being God, also both Christ is God and Holy Spirit is God, not three Gods but Three Hypostases in one God, and if so, then all Three are also saviors.
Not a single, not even a tiniest promise of God the Father was or better could be fulfilled outside Christ, as Paul vocally asserts: 2 Cor. 1:20: "For all the promises of God in Him [i.e. Christ] are “yea”; and in Him “amen” unto the glory of God by us".