IT is a big weekend for the Murphy boys, currently of Hongkong and Macau via, Tralee and New York. That's Declan and Joe, of course, while mother Murphy is also on hand, just hoping to see her boys succeed once again at what they are rather good at - winning horse races. Declan is a five-year veteran of the Hongkong racing scene who says goodbye to it all at the end of June but only to take a jetfoil ride across the Pearl River to link up with Joe. He is the excellent young trainer who saddles up Rock N Roll in tomorrow's $1 million Otard XO Macau Derby with brother Declan, while mother watches from the stands to cheer a hoped-for Classic triumph. And Declan has his own work to do today on Gold Cup Day at Sha Tin. He is back refreshed after a break of three days - unwanted though it was. Jockey Murphy was stood down by the Stewards on a controversial careless riding charge but took part of the time off to freshly run the rule over Taipa where he will be riding next season. The Licensing Committee of the Jockey Club has stated that they will oppose any application from Declan by invoking the three-year expatriate rule but that's not a worry to the former champion apprentice of New York. ''I had no intention of applying for next season because it was always my intention to link up with Joe at Taipa. We discussed it at length and it is something we are both very keen on. ''I think he has done a magnificent job in his first season as a trainer and he has a lot of horses and, hopefully, more to come. We have always got on very well together and, of course, he came out here in my early days to keep me company. ''It's certainly a big day for him - and I was rather hoping he might keep Rock N Roll until next season for me! He would have been a good thing in Class Four,'' smiled Declan. Murphy's departure from the Hongkong scene is not unexpected, given the rules of the Jockey Club, but he will be missed. Not that he is finished - not by a long chalk. ''There's almost three months of the season left and I am looking for a lot more winners. I want to end my Hongkong career on a high note and I am sure there will be quite a few chances,'' he says. ''It has been a tremendous few years here and I am pleased to be staying in the region although really I have very little choice. I do have weight problems and riding in America would be impossible,'' says Declan. Those who know him well will certainly testify to that. Lunch and dinner at the Murphy household is not exactly lavish. Salad followed by salad . . . followed by, yes, salad. ''It's not the world's most attractive diet but if you want to ride racehorses and you happen to be built like me, that's what you have to do,'' he says. Declan swings back into action today with a couple of interesting rides for his old pal Derek Cruz. They go back to the early days with Eddie K. C. Lo who first brought Murphy to Hongkong from New York. He had been there since his father - a former top flight jump jockey - and mother emigrated to America from Ireland. He was born in the western Ireland town of Tralee - and has paid a number of visits back there in recent years. But it is all business today as he takes out improving Blue And Gold in the Victoria Racing Club Trophy and progressive Our Pal in the final event. The VRC Trophy may not rank quite as highly in the Murphy family's ambitions this weekend as the Macau Derby but it is still a tasty piece of silverware and Declan can go close. But his comeback winner could be in the nightcap where Our Pal must measureup to another rise in class. ''He is a nice horse and it is a pleasure to ride him for Derek who has been very good with rides coming my way. I thought he won quite well last time and we did come a way clear which is encouraging. ''He may still be learning about the game and that makes it a bit tougher when you get into better company. But it's one I would like to be winning,'' he says. No sooner will he have stashed away the riding gear after the final event than Declan takes the well worn path to Macau for tomorrow's Derby. And that is where Joe and another old pal, former Hongkong-based rider Danny Brereton, take over the limelight. Rock N Roll is the horse they believe can do it - but no Derby is easy to win. Says Joe: ''I am very pleased with him. He was bought for the Derby and he has done just about everything right. I have got him to the best I can and I just hope that he lives up to our expectations. ''I have had a great season and I am just delighted it has gone so well. I have had the support of a lot of loyal owners, people who stuck with me from my days as Nat Chan's assistant and that has meant a lot. ''You can't help thinking about winning the Derby, after all it is the most important race in any calendar. I don't think about it all the time but it pops into your mind now and then. ''And from now until the race is over I won't be thinking about much else,'' said Joe last night. The tightly-knit Murphy family are hoping to really celebrate this weekend and there have been good luck telegrams from other members of the clan back home in New York. Despite their relative youth, both Declan and Joe have seen plenty of the world - and certainly made their mark. The champagne will be flowing tomorrow night if things go as planned. It may not be the brothers' most favoured tipple. But it is easier to get than Guinness.