The oddity about last night's Jockey Challenge betting was the missing name of one of the Valley's brightest lights - Brett Prebble. For reasons that appear to be nothing more than an inexplicable glitch, Prebble has turned up at the midweek venue with only three rides, and Jockey Club odds makers could not even find a space for him in the list of 13 'name' riders involved at the meeting. Instead Prebble, usually the one punters are most likely to support to topple perennial favourite Douglas Whyte, finds himself in the Challenge no man's land - the 14 bracket called 'others'. He's swapped places with emerging apprentice Derek Leung Ka-chun, who rode his first double since returning home from his further riding experience in Australia at Sha Tin on Sunday. Leung has five mounts - three of them for Me Tsui Yu-sak, who supplied his first three winners - and one each for Gary Ng Ting-keung and his allocated trainer Paul O'Sullivan. Leung is an outsider at 40-1, but the fact he can muscle into the list of leading riders at the expense of one as senior and successful as Prebble is yet another sign that this young man's star is on the rise. The odds makers have the Challenge as a head-to-head between Whyte at $3.00 and Darren Beadman at $4.00. But Whyte has the advantage in terms of quality and quantity over Beadman and looks the better value, despite the slightly more cramped odds. Whyte has a full book of eight mounts, starting off with the useful Fortune Gallop as one of the better chances in the Class Five mile. He then handles Big Kahuna for O'Sullivan and Magic King for Andreas Schutz, with the awkward barrier (nine) being the major obstacle for the Durban Demon to overcome on the latter galloper. Moody Super Surprise can bounce back to his best for David Ferraris in the fourth event, decided over the same course and distance as his lone win. Significantly, we are only two weeks off the anniversary of that win, achieved from an inside gate for Christophe Soumillon on International Jockeys' Series night. O'Sullivan's Super Snippets has a sound each-way chance in race five, while Many Gains (race seven) and Holy Ravioli (race eight) are superior winning chances.