Rock Sand followed up his Derby win with a run at Royal Ascot where he took the St. James's Palace Stakes over one mile from three "moderate" opponents at odds of 1/10. He then faced older horses for the first time when he was sent to Sandown for the Eclipse Stakes. The 1903 running of the Eclipse Stakes on 17 July was one of the notable races of the early 20th century when Rock Sand faced the previous year's Derby winner Ard Patrick and the filly, Sceptre who had won the other four British Classic Races in 1902. The race thus brought together "the three best horses in England", and perhaps "the most valuable field of horses that ever started in a race in any part of the world". The King was among the immense crowd which was drawn to Sandown for the "Battle of Giants". The odds at the start were 5/4 Rock Sand, 7/4 Sceptre and 5/1 Ard Patrick. Rock Sand disputed the lead with Oriole in the early stages but was challenged and overtaken by Ard Patrick before the turn into the straight. He faded in the closing stages and finished third, beaten a neck and three lengths by Ard Patrick and Sceptre who fought out a "desperate finish". The contest was favourably compared to the race for the 1887 Hardwicke Stakes between Ormonde, Minting and Bendigo.