Royal Opera House, who will race in the United States for the first time in Saturday's sixth race, has undergone several changes since his last start in March.

Royal Opera House (6) was gelded in May and will be treated with Lasix for the first time. Now trained by Dan Blacker, Royal Opera House will race on turf for the first time.

The 3-year-old, by Royal Applause, had one win in three starts in England  - a maiden race at seven furlongs at Chemlsford City (not far from London) on Dec. 8. Prior to that, he was seventh of 13 in a lowly-rated maiden race at Southwell last November.

In March, Royal Opera House was last of 10 in a six-furlong handicap on the all-weather surface at Newcastle, his only start this year.

It all adds up to a difficult assignment for Royal Opera House in his American debut. He is 15-1 on the morning-line and faces a difficult job beating runners such as Sorry Erik (4) and Marckie's Water (5).