Roberto Castro leads The Players Championship by three shots after a blistering nine-under-par opening round of 63 on Thursday. American Castro, in his first appearance at TPC Sawgrass, made light of the venue&aposs fearsome reputation, sinking seven birdies and an eagle to equal the course record and sit clear at the top of the leaderboard on day one of the prestigious PGA Tour event in Florida. He leads ahead of countryman Zach Johnson and world number two Rory McIlroy, who are tied for second at six under. An all-American group of six players hold a share of fourth at five under, including world number one Tiger Woods and US Open champion Webb Simpson. Swedish duo Henrik Stenson and David Lingmerth are a shot further back, tied for 10th at four under. That group includes Ireland&aposs Padraig Harrington, Australian Greg Chalmers, Spaniard Sergio Garcia and South Korean Sang-Moon Bae, as well as American Jason Bohn. Chalmers&apos compatriots Jason Day and Adam Scott – the latter making his first competitive appearance since winning The Masters at Augusta last month – are tied 17th at three under. Vijay Singh announced this week he is set to sue the PGA Tour for damage to his reputation and loss of earnings following a ban for using performance-enhancing drugs found in a deer antler spray, which was later rescinded. The Fijian is in danger of missing the half-way cut, as is big-name American Dustin Johnson after both men struggled to two-over rounds of 74 on Thursday. Englishman Ian Poulter and Australian Geoff Oglivy fared even worse, as they turned in three-over 75s. Of the other Australians in the field, Matt Jones in tied 34th at two under and Marc Leishman holds a share of 68th following an even-par 72. Robert Allenby and John Senden had to settle for one-over 73s to be tied 86th, while Aaron Baddeley is set to miss the weekend after a disastrous six-over 78.