Aidan O'Brien has warned any potential rivals to Diamond Necklace (St Mark's Basilica) in the G1 Qatar Nassau Stakes that his unbeaten filly may yet have more to offer, with the Ballydoyle trainer also preparing to bring over Gstaad (Starspangledbanner) and Scandinavia (Justify) as part of a formidable squad for the Qatar Goodwood Festival.A three-time winner as a juvenile, culminating with a first Group 1 win in the Prix Marcel Boussac, Diamond Necklace heads to Goodwood searching for her fourth consecutive top-level success, having kicked off her three-year-old campaign with a clean sweep of the fillies' Classics in France.An impressive three-length winner of the Poule d'Essai des Pouliches, the daughter of St Mark's Basilica then showed her battling qualities when following up by a short neck in the Prix de Diane, with O'Brien viewing the Nassau Stakes (Thursday, July 30) as the obvious next step after she proved herself over a mile and a quarter at Chantilly.“We stepped her up to a mile and a quarter last time and we felt we would stay there for the minute,” O'Brien explained in an interview with Goodwood Racecourse. “We were very happy with her. She's doing very well, physically. She obviously has a great pedigree, and she's by St Mark's Basilica, so she's exciting.“She looks very good at the moment. Everything she's been asked to do, she's done very easily and very comfortably. She is obviously in that 'could be anything' category. She looks really special at the moment and we're very excited to have her.”The first of the Ballydoyle big guns into battle will be Scandinavia when he attempts to win the G1 Al Shaqab Goodwood Cup (Tuesday, July 28) for the second year in succession.Having underlined his standing as the leading stayer in training with a hard-fought success in the Gold Cup when last in action, the son of Justify now faces a rematch with Trawlerman (Golden Horn) after that epic clash between the pair at Royal Ascot, with just a head splitting them at the line.“I think it will be interesting [reopposing Trawlerman], but I think that is him, whether the trip is a mile and a half to two and a half miles,” O'Brien continued. “He'll never win by very far – he just does enough.“It's very hard to gauge how much is in there and that's the way he has always been. He's very like Yeats in that way; he's a high tempo horse and finds it very easy to go a high tempo for a long time.“Everything has gone well with him since [the Gold Cup], and all this year as well. We were delighted with him at Ascot. He's in good form.”Completing the leading players for O'Brien at Goodwood will be his Irish 2,000 Guineas hero Gstaad, who will also face a familiar foe in George Boughey's Bow Echo (Night Of Thunder), having occupied the runner-up spot behind that rival in both the 2,000 Guineas and St James's Palace Stakes.Round three between the leading three-year-old milers of their generation will take place in the G1 Visit Qatar Sussex Stakes (Wednesday, July 29), with O'Brien optimistic that this could be Gstaad's turn to have his day in the sun.“He ran a good race at Ascot and we were delighted with him at the Curragh,” said the trainer. “He came out of it very well and we're looking forward to going there with him – we always thought it was a race that would suit him.“He obviously just failed at Ascot. It didn't really work perfectly for him on the day, but he still ran a great race. We're looking forward to the race again. Hopefully, Bow Echo runs and it will be a good race.”He continued, “In the Guineas, we felt we were forced on. We were very forward and had to do our own donkey work, while Bow Echo had lovely cover and everything worked well for him.“Then we went to Ascot and felt that maybe it didn't go 100 per cent for us, either. Maybe the lads thought it didn't go perfectly for Bow Echo, either. It's going to be interesting. That's what I think makes these races great. We're looking forward to seeing what happens.”O'Brien, who is set to be double-handed in the Sussex Stakes, with Puerto Rico (Wootton Bassett) expected to join Gstaad in the line-up, also welcomed the increase in prize-money for the Group 1 feature to £1.5 million, making it Europe's most valuable mile raceHe added, “I think it's vital [the prize-money]. That's what brings good horses to the races, and good horses bring the crowds, the spectators and the people to the races and those big meetings.“It's all about the prize money. It's such an expensive game – to buy a horse, train a horse and do everything with a horse. I think it's vital. Hats off to them. Obviously, they get it. It's very important and very exciting.”The post Diamond Necklace ‘Could Be Anything’ Warns O’Brien Ahead of Nassau Tilt appeared first on TDN | Thoroughbred Daily News | Horse Racing News, Results and Video | Thoroughbred Breeding and Auctions.