Shortly after his signing, it was announced that Adam Ottavino would wear number 0. When he takes the field, he will become the first ever Yankee to wear the number. That leaves just 20 numbers under 100 that have never been worn by a Yankee player. Five other numbers have been issued to just one player in team history, only one which is retired: Lou Gehrig’s #4.
On a long enough timeline, the Yankees will probably eventually have to dip into triple digit numbers. They’re not in any danger of running out of numbers under 100 any time soon, but it may happen eventually.