ARCADIA, Calif. (AP) _ Siphonic, considered one of the leading Triple Crown contenders when the year began, won't run in the Kentucky Derby due to soreness in his right front ankle.

``He's doing fine, we're going to give him some R and R for a couple of months,'' assistant trainer Michelle Jensen said Friday.

Jensen said Siphonic will probably return to racing in late spring, meaning it's unlikely the Kentucky-bred son of Siphon will run in the other Triple Crown races _ the Preakness on May 18 and the Belmont Stakes on June 8.

Siphonic established himself as a leading Derby contender late last year by winning the Lane's End Breeders' Futurity and Hollywood Futurity and finishing third in the Breeders' Cup Juvenile.

He finished second behind Labamta Babe in the $150,000 Santa Catalina Stakes on Jan. 19 when he stumbled badly at the start of the 1 1-16 mile race, and was third as the 2-5 favorite in the last Sunday's $250,000 San Felipe Stakes _ the final prep before the $750,000 Santa Anita Derby on April 6.

``He just came out of that race a little sore, so we decided that instead of pushing the horse we'll give him a little time off,'' Jensen said.

Siphonic, who has won three of six lifetime starts and earned $763,978, led the 1 1-16 mile San Felipe at the top of the stretch before tiring and finishing behind Madaglia d'Oro and U S S Tinosa.