Rachel Alexandra has been ruled out of next month’s planned showdown with Zenyatta.

Rachel Alexandra, the first filly to win the Preakness Stakes for 85 years, will not run in the Belmont Stakes next week.

Curlin, the 2007 American Horse of the Year, will be retired to stud in 2009.

Curlin has the opportunity to break the all-time American earnings record held by Cigar in Saturday’s Jockey Club Gold Cup at Belmont Park.

Connections of imperious Dubai World Cup winner Curlin are considering a crack at the Prix de l’Arc de Triomphe later in the season.