The American and European Ryder Cup teams have begun practice rounds at Louisville's Valhalla Golf Club.The bienniel competition begins Friday.Former PGA pro and current NBC golf analyst Johnny Miller says the Americans once again come into the matches as underdogs."The U.S. has only won one time in the last 14 years and that was the miracle at Brookline, so, the U.S. was 13 in a row on American soil and the U.S. has lost three out of the last four in the U.S., and those are the stats, especially the last one, that really hurt, because you don't want to give up home court advantage, so to speak," Miller said.The Ryder Cup is played on alternate U.S. and European courses.The Americans will be without Tiger Woods, who's recovering from surgery.