Can you name these players?

First day at Yankees camp

In rainy Tampa for a five-day stint filling in for E-Boland.

First thing I notice: the uniform numbers the Yankees did not hand out this spring.

6
18
21
35
51
55

And then some high numbers that are used by non-players.

Can you name all of the former Yankees who are being honored by their uniform numbers not being given out even though the numbers are not retired? Of those six, which do you think will eventually have their uniform numbers retired?