There has been no such admission on the part of the Orthodox church (if any individual Orthodox, whether clergy or laity said that, it would not count, for the only definitive statements of Orthodox doctrine are contained in the Ecumenical Councils and the prayers and hymns of the Orthodox Liturgy, both the Divine Liturgy and the Divine Office (Vespers, Matins, etc, indeed, daily Matins contains the most information of any of the Orthodox services overall, although the most important parts of the Orthodox faith are encoded in the invariant text of the Divine Liturgy, which is the same whether celebrated on Saturday, Sunday or a weekday, and also the propers, that is, those parts which do change on each day of the year, such as the appointed Scripture lessons).
The worship of the Orthodox on Saturday continues and the worship on Sunday, which by the way has also always been a day of worship for the Jews, since the Jews actually pray in the Synagogue not just on Friday evening and Saturday morning but indeed have services every day a week, any time they have a Minyan (a quorum of ten Jewish men who have had their Bar Mitzvah; our Lord has established for Christians a minyan of two (“Wherever two or three are gathered together in my name, there I am in the midst of them”) for corporate worship.
The extreme importance of Sunday worship however is fully Scripturally justified, for as the Gospels make clear, our Lord rose from the dead on Sunday. Indeed this is prophesized in Genesis 1:3-5 , for Jesus Christ is the Word, the Way, the Truth and the Light according to the Gospel of God, and thus, Let there be Light.
Indeed Luke 24:13-48 makes it quite clear that Genesis 1 is as much a prophecy of the passion and resurrection of Christ and His recreation of the world, as He destroyed death and will make all things anew, as it is of the original creation.
