Douglas Whyte is the clear market leader in today's Jockey Challenge, but with the wind of the John Moore stable in his sails, Weichong Marwing can beat the champion and also provide players with significantly better value. On last night's market, Whyte was a short $2.2 favourite for the Sunday city venue Challenge, with Marwing a clear second elect at $3.5. Boom apprentice Matthew Chadwick is on the third level of favouritism at $8.0. Whyte has been in tremendous form and last week rode a treble to notionally dead-heat with Chadwick on the Sha Tin Jockey Challenge at 36 points apiece, only to be separated by a countback, which gave the nod to the junior rider on the basis of two fourth placings. Today, Whyte has rides in nine of the 10 races with some strong chances and, as always, must be afforded great respect. But there's not much margin there for punters at last night's short quote. Marwing looks the better play. He has a doubtful ride in the first and no mount in the second, but could get early points with My Time for Dennis Yip Chor-hong in the third. It's at the back end of the programme when Moore's horses in Class Three or higher are engaged. Ever Beauty (race six), Willing Storm (race eight), Fortune Haven (race nine) and Classic Reunion (race 10) look to be winning chances, and so does the consistent Operation Secret for Derek Cruz in the seventh. Derek Leung Ka-chun is also a winning proposition at double-figure odds, with a full book of 10 rides. He has ridden 19 winners so he is good value for his 10-pound allowance, which can be claimed all day even if he rides his 20th winner early on the programme. Meanwhile, a new rule for the Challenge betting goes into effect today. If any jockey is replaced for any reason after the official start of betting (5pm the day before), the substitute jockeys do not score points if/when any of those late pick-up rides win or place.