Since Churchill Downs held its two Stars of Tomorrow cards last fall, 24 of the horses that competed on either day went on to win stakes races, including 15 that won graded races. Those are very impressive numbers, and it’s sufficient reason for racing fans and horsemen to be enthused when Churchill kicks off its 21-day fall meet Sunday with the first of its two Stars of Tomorrow all-2-year-old programs for 2017. Four stakes and huge fields of maidens comprise the bulk of an 11-race card that starts action at the historic track in Louisville, Ky., where five-day race weeks will run through Nov. 26. Mondays and Tuesdays are dark, with post time on most racing days set for 1 p.m. Eastern. The opening-day stakes, all on the main track, are two sets of twins: the $80,000 Rags to Riches (race 8) for fillies and $80,000 Street Sense (race 10) are open one-mile races, while the $200,000 Spendthrift Juvenile Stallion (race 7) and Spendthrift Juvenile Filly Stallion (race 9) are seven-furlong events restricted to offspring of Spendthrift Farm sires. Those races kick off a stakes schedule that will culminate as usual with the most important races during the final week of the meet. In all, 15 stakes worth more than $2.5 million are on tap, peaking on Nov. 24 with the 143rd running of the Grade 1, $500,000 Clark Handicap for 3-year-olds and up. Other notable stakes include the Grade 2 Falls City on Thanksgiving Day, Nov. 23 (post, 11:30 a.m.), and twin 2-year-old events, the Grade 2 Kentucky Jockey Club and Grade 2 Golden Rod, set for the second Stars of Tomorrow card on Nov. 25. For Breeders’ Cup weekend, Churchill will intersperse its live racing with the simulcasts from Del Mar. The Friday card starts at 2 p.m. and the Saturday card at 2:15. Churchill racing secretary Ben Huffman expects purses to average about $535,000 per day at this meet, while the per-race average will be about $42,000, 30 percent more than in 2012, when the September meet did not yet exist. Including bonuses from the Kentucky Thoroughbred Development Fund, purses for maiden-special races will be worth $60,000, while allowances range from $62,000 to $72,000. All four opening-day stakes are part of a 20-cent Single Six wager (races 6-11), which has gained popularity in recent seasons at Churchill. The Single Six is one of a multitude of exotic wagers offered daily. Corey Lanerie, the leading jockey at 14 of the last 16 Churchill meets, heads another highly accomplished riding colony, while Steve Asmussen, Mike Maker, and Brad Cox can be expected to vie for top honors among trainers. The Stars of Tomorrow program, first run in 2005, has produced such major winners as Rachel Alexandra, Super Saver, Shackleford, Fort Larned, and Gun Runner. Among the horses to participate last fall were Dream Dancing, Sailor’s Valentine, McCraken, and Farrell. Field size at the fall meet typically surpasses the spring and September numbers. Last fall, fields averaged 9.0 horses per race, while 8.1 and 8.9 were the respective averages for the first two meets this year. Travis Stone will be back in the race-caller’s booth, and Joe Kristufek will be providing pre-race analyses and post-race interviews.