LOUISVILLE, Ky. &ndash; In the vast majority of horse races, there are question marks among the past performances of the entrants, ranging anywhere from whether a prospective runner can handle an untried distance to perhaps another&rsquo;s potential effectiveness with a change in racing surface.\r\nFriday&rsquo;s Grade 3, $500,000 Breeders&rsquo; Cup Marathon at Churchill Downs presents those specific unknowns, plus a whole lot more. At 1 3/4 miles on dirt, the race is atypical, and the outcome appears as murky as the Ohio River that flows past downtown Louisville.\r\nAmong the unanswered questions of the Marathon: Can relative no-names Bright Horizon and Precision Break extend the dominance of Europeans in this race or will racing over a traditional dirt track at Churchill neutralize the effectiveness of the Europeans the way the synthetic Pro-Ride surface at Santa Anita did not in the two prior runnings of the Marathon?\r\nWill Prince Will I Am transfer his sharp current form to dirt after winning the Grade 1 Jamaica at 1 1/8 miles on turf?\r\nAnd who holds the advantage, dirt marathoners with experience in mid-level stakes races, such as Eldaafer and Alcomo, or those tested against higher-class opposition, but not in such demanding stamina tests, most notably Grade 1 Hollywood Gold Cup winner Awesome Gem?\r\nThese questions and many others in the 12-horse Marathon require guesswork from horseplayers, and and the befuddling nature of the race is reflected in the morning line. Track oddsmaker Mike Battaglia made Awesome Gem a narrow favorite at 7-2, followed by co-second favorites Price Will I Am and Giant Oak at 4-1 apiece, A. U. Miner at 9-2, and Alcomo at 6-1.\r\nThe only obvious fact in the Marathon is that Awesome Gem is the most accomplished entrant. He has made over $2.2 million, far more than second-leading earner Giant Oak&rsquo;s bankroll of just under $598,000.\r\nA 7-year-old Awesome Again gelding owned by West Point Thoroughbreds, Awesome Gem won the Grade 2 San Fernando in 2007, the Grade 2 Hawthorne Gold Cup in 2009, and the Grade 1 Pacific Classic this July over Rail Trip.\r\nThis will be his fourth consecutive appearance in the Breeders&rsquo; Cup. He ran third behind Curlin in the 2007 Breeders&rsquo; Cup Classic, edging Street Sense for the show position; finished sixth in the 2008 Breeders&rsquo; Cup Mile behind Goldikova; and ran seventh behind Zenyatta in the Classic last year.\r\nSuffice to say, there are no horses like Curlin, Goldikova, or Zenyatta in the Marathon.\r\nIt was the opportunity to race against easier company that weighed into the decision to run Awesome Gem in the Marathon rather than against a better cast in the Dirt Mile, trainer Craig Dollase said.\r\nAfter making his last three starts on synthetic tracks, Dollase is optimistic Awesome Gem will move forward switching to race on dirt, over which the horse has compiled a 4-4-2 record from 12 starts.\r\n&ldquo;His numbers are very good on it,&rdquo; he said, alluding to his speed figures.\r\nRegular rider David Flores has the mount on Awesome Gem, who since winning the Hollywood Gold Cup has recorded a pair of rear-half finishes in the Grade 1 Pacific Classic and Grade 1 Goodwood.\r\nAlcomo, one of two supplements, along with Prince Will I Am, cannot match the r &eacute; sum &eacute; of Awesome Gem, but is a proven marathon dirt horse.\r\nAnother 7-year-old, Alcomo is among the most well-traveled in the field, racing from Brazil to Dubai to America. But it is here in America where he has amassed the bulk of his earnings.\r\nIn each of the last two years he has won marathon stakes at 1 1/2 miles, taking the Greenwood Cup at Philadelphia Park in 2009, and the Grade 2 Brooklyn this year at Belmont over Marathon longshots Gabriel&rsquo;s Hill and Eldaafer.\r\nFollowing the Brooklyn this year he finished a close second to upsetter A. U. Miner in the July 17 Greenwood Cup. He is unraced since because of a lack of suitable dirt marathon preps, trainer Eduardo Caramori said. Rafael Bejarano has the mount.\r\nFour-year-old Giant Oak &ndash; runner-up in his last two starts, the Grade 3 Washington Park Handicap, and the Grade 2 Hawthorne Gold Cup &ndash; should benefit from the return to Churchill Downs, where he has performed well in three starts. A son of Giant&rsquo;s Causeway, he ran second in the Grade 2 Kentucky Jockey Club at 2, followed by a close fourth behind Blame in the Clark Handicap last fall, and another fourth behind Blame in the Grade 1 Stephen Foster this summer.