[CentOS] script help - '3rd last field'

> I am pretty sure there is a way in awk to figure out how many fields
> you have, then take the total # of fields -3 each time to get the
> third last one.  Just heading out the door and off hand can't remember
> how it would be done.
>
>   

i can do it in cheetah templating with

set myloc = $getVar("hostname","")split('.')[-3]

the -3 says the last 3rd field in the string - i need the same so maybe 
awk can do this