[2] Doris was a poor racehorse who never rose above selling company,[3] but proved a highly successful broodmare: in the year of Sunstar's Derby win she produced a filly named Princess Dorrie who won the 1000 Guineas and The Oaks in 1914.

[5] In the winter and early spring of 1911, Sunstar began to make rapid progress and Morton decided to test the colt in a private trial race at Wantage.

[6] News of the supposedly private trial soon became public, and when Sunstar appeared at Newmarket for the 2000 Guineas twelve days later, he started the 5/1 second favourite in a field of fourteen runners.

[8] Two weeks after his win in the Guineas, Sunstar was moved up to ten furlongs to run in the Newmarket Stakes, despite the concerns of his trainer, who felt that the unusually hard ground presented a risk of injury to the colt's legs.

He had sustained an injury to the suspensory ligaments or the "back tendons"[12] so painful that he was unable to put any weight on the injured leg, making his participation at Epsom extremely doubtful.

[13] He was able to deal with the superficial lameness, but informed Joel that the underlying condition remained and that although Sunstar would be able to run in the Derby, any further aggravation of the injury would almost certainly end the horses career.

[6] In the build-up to the race there were rumours that Sunstar was the target of a plot to prevent his running, orchestrated either by Joel's personal enemies or by unscrupulous bookmakers who stood to lose heavily if the colt were successful.

[16] The field was considered weaker than usual, with several of the year's best colts missing the race, including the City and Suburban Handicap winner Mushroom, who had never been entered.

George Stern settled Sunstar in fourth or fifth place behind Bannockburn, Phryxus and Eton Boy, until the turn into the straight when he sent the favourite through a gap on the inside to take the lead.

[22] In reality, the colt showed some signs of recovery[23] and was being prepared for the St Leger at Doncaster in September when he broke down again in training in August and was then retired to stud.