Disk format of Raid 5 volume issue

Cannot use non raid formatted disk to replace a Raid 5 disk volume.

Background to issue:
I have a Raid 5 configuration on my PR4100 with 4x4TB WD Red drives installed as well as a spare 4TB WD Red drive that I want to use a a recovery disk in the event one of my the Raid volumes needs to be replaced. The spare drive was previously formatted as a JBOB disk and will not reformat when installed as replacement of one of my Raid 5. I assume it needs to be reformatted to meet format requirements for a Raid 5 configuration.

What is the disk format requirements for the Raid 5?
Can the format requirements be created using the MAC OS? If not, is their an alternative method using the PR4100 built in functions.

Just delete all the existing partitions.

With SSH access, you can wipe the partitions right on the PR4100 with gdisk.
First identify your disk among the block devices

df -h

Your disk is usually one of sda / sdb / sdc / sdd
Make sure all partitions of your disk are unmounted
Replace sdX with the correct device

umount /dev/sdX1 /dev/sdX2 /dev/sdX3

gdisk /dev/sdX
p        (print partition table to double check)
x        (enable expert options)
z        (destroy all partitions)
w        (save changes)

Warning: you cannot recover the data on the selected disk. Use at your own risk.