Christ in His high priestly prayer specifically states, "I am not praying for the world, but for those you have given me" (John 17:9). That is what He said; it only remains to learn by reverent comparison with other Scripture just what the words mean.
To insist that by these words Christ meant that He never prayed for sinners would be to read into the words more than is there. We must remember that these words were spoken in a particular context; the great High Priest was appearing before the throne of mercy as Advocate and Intercessor and could at that time include in His prayers only those who were His own.
When a high priest of the Old Testament appeared before the mercy seat to offer blood for the sins of Israel, his intercessions extended to Israel only. They were the only ones for whom that atonement was made. They were the only ones who trusted in Him and looked to Him for help. Christ came in fulfillment of the Old Testament type, and it may safely be assumed that the prayer of John 17 was made only for those who accept Christ's atonement and avail themselves of the protection it affords.