Are you sure? My understanding is that because we have chosen to have one less on the main list we can promote a player at anytime regardless.No.
The rule is he can only be upgraded to main list during two windows : At the completion of the NAB challenge and before RD1 and at the mid-season break.
He cannot be promoted before the NAB or any other time other than above.
Of course that excludes LTI's for which upgrades can be done at anytime.