Mine

update 
  day245stats 
set 
  rank=r.srank_today, 
  rating=r.rating_today
from
  rollingstats as r
where 
  r.serverid=day245stats.serverid 
 and
  r.playerid=day245stats.playerid

                                           QUERY PLAN                                            
-------------------------------------------------------------------------------------------------
 Merge Join  (cost=8712687.23..8922847.43 rows=159748 width=145)
   Merge Cond: (("outer".playerid = "inner".playerid) AND ("outer".serverid = "inner".serverid))
   ->  Sort  (cost=2246825.77..2258949.80 rows=4849611 width=137)
         Sort Key: day245stats.playerid, day245stats.serverid
         ->  Seq Scan on day245stats  (cost=0.00..149925.11 rows=4849611 width=137)
   ->  Sort  (cost=6465861.45..6523297.15 rows=22974280 width=24)
         Sort Key: r.playerid, r.serverid
         ->  Seq Scan on rollingstats r  (cost=0.00..521831.80 rows=22974280 width=24)