Brett Prebble and Olivier Doleuze were the only positive market movers in last night's early Jockey Challenge betting, but in Prebble's case his fans are banking on the Australian's renowned ability to offset bad barriers. Race after race at Happy Valley this afternoon, Prebble must weave a substantial amount of magic to negate wide alleys, and any failure to do so will be the difference between victory and defeat in many instances. Prebble leads the early season jockeys' championship on 13 wins, but a rampaging Douglas Whyte has cut right into his tally with a sparkling four-timer at Sha Tin last Sunday. Doleuze has had a quieter start to the new term but hit form with a vengeance on Wednesday night, taking the Jockey Challenge in a surprise result after being downed at a considerably tighter price at Sha Tin three days earlier. Doleuze may even set his rivals a target to catch this afternoon, as he has claims in the first three races with Wong's Success for Francis Lui Kin-wai (race one), Freebird for Derek Cruz (race two) and Happy Go Lucky for 'king of the Valley' Caspar Fownes in the third. The Frenchman has rides in eight of the 10 races, and most of them have the potential to be in the placings, with the possible exception of the disappointing Win-A-Lot. In last night's early markets, Doleuze had been backed from HK$7.00 into HK$6.50, with Prebble the best supported from HK$5.00 into HK$4.00. Lack of demand at a short price had seen Douglas Whyte drift from HK$1.90 to HK$2.10.