The old conundrum of the relative importance of rating versus form is about to get another airing, with the in-form Flying Tamari trying to force his way into the final field of 14 for the HK$14 million Mercedes-Benz Hong Kong Derby on March 18. Theoretically, the 14 top-rated horses for the Derby would be the 14 colts or geldings to make up the final field. But the conditions of the race provide for some discretion from the selection committee, and the two factors that demand their attention are the strength of form and a capacity to manage the Derby distance of 2,000 metres. Now one would think that common sense would sort these things out almost automatically with three sensible filters - ratings, form and proven ability at the distance - but it's amazing how outside issues, sometimes of a political nature, can creep in to undermine sense, which is nowhere near as common as the term suggests. The near miss of Absolute Champion from the Cathay Pacific Hong Kong Sprint field on December 10 is the most recent glaring example. Here was a very much in-form sprinter, a last-start record breaker over the course and distance being left out of the original field. Meanwhile, on a higher rating, 1,000m specialist Natural Blitz was given a place in the field, even though officials knew he would be a massive price and absolutely zero chance of running a strong 1,200m in such elite company. Absolute Champion did eventually make the Hong Kong Sprint field and it's history now that he smashed his course record, turning in the world's number one performance for a sprinter in 2006. And unless you count yourself among the owners, trainer and jockey of runner-up Silent Witness, what a tragedy it would have been if Absolute Champion had been at home in his box while Natural Blitz laboured home in 11th place, beaten 17 lengths. Back to the Derby, and the most obvious horse begging for elimination on the strength of current form is expensive private purchase Puerto Rico, a Sadler's Wells colt who is now with Derby-winning trainer Tony Millard. Puerto Rico had six starts in England and Ireland for two wins and two thirds, but earned his high rating from his third to Youmzain in the Group Two Great Voltigeur Stakes over 12 furlongs (2,400m) on soft ground during the York festival on August 22. When you go back and look at Puerto Rico's form more closely, you quickly find his Achilles heel - firm tracks. In two starts on good ground, he ran 10th of 13 in the Irish Derby and last of nine in the Grand Prix de Paris, beaten 14 lengths and 81/4 lengths respectively. Now exactly why a potential purchaser would think this horse to be well suited on Sha Tin's typically good-firm ground at 2,000m in the Hong Kong Derby is anyone's guess, but the evidence of his first two local starts is that he's having grave difficulty measuring up. He has run last on both occasions, behind Gold Striker in a Class One handicap over 1,400 metres and, more tellingly, in the Hong Kong Derby Trial (1,800m) behind Floral Pegasus, this time beaten 12 lengths. Puerto Rico now has a domestic rating of 94 and remains in contention for Derby selection. He's entered for the Hong Kong Gold Cup on Sunday and another failure would probably see his rating drop below the Derby selection threshold, and save everyone the trouble and/or embarrassment. But the very thought that a quality, consistent and in-form horse like Flying Tamari could miss out after being first past the post at three of his last four outings and having form at the required distance, while Puerto Rico is currently qualified, is cause enough for concern.