It's already offline, so there is no need to force it offline before removal. You need to force offline your pred fail drives (1:8) before removal/replacement though.
I have a drive failure and a predicted drive failure on one of our PowerEdge servers.  I have an offline option for all the drive except for the full drive failure one... I have the option for the predicted drive failure.   Looking at the screen shot below, it seems the full failure drive (2) has already been removed from the RAID and my Hot Spare has been resourced. What is the best way to proceed here?  [IMAGE] 
PowerEdge Drive Failure - no offline option