Average without Duplicate Values

I have a predictive model for MLB games. I use the following formula to take averages of the last four numbers in a single column. But the numbers I am using are duplicates. I would like to keep this formula, but have it disregard the duplicate values. Is that possible? Thanks in advance.

=IFERROR(AVERAGE(OFFSET(INDEX(B2:B163,AGGREGATE(14,6,(ROW(B2:B163)-ROW(B1))/(B2:B163<>""),1)),0,0,MAX(-COUNT(B2:B163),-4),1)),0)

Average Without Duplicates.xlsx