Let's start with a hard level.
Here are the nicknames of the 25 Cubs participants without their jersey numbers, although a hint would be that they are in jersey number order.
To add another hint, here is the original graphic I found with the jersey numbers:
Knowing the Cubs roster, a lot of these are variations on their real names, which makes it a lot easier.
Still stuck on few? How about a name bank to work with? (With two extra names for the party poopers with no nickname)
Edwards Jr., Carl
And drum roll please..........here is the answer key:
Jon Lester and Tommy LaStella were the non-participants from the name bank, just using their last names.