Rachel Alexandra’s undefeated season in 2009 won her Horse of the Year honors and electrified a down-on-its-luck industry. Though the sensational filly is leaving racing’s stage, a future breeding date with another superstar could make things interesting.

Having won only two of five races this year, Rachel Alexandra was retired yesterday, with co-owner Jess Jackson saying it was time to "reward her with a less stressful life." He said she would be bred to Curlin, the 2007 and 2008 Horse of the Year, at Jackson’s Stonestreet Farm in Lexington, Ky.

"Imagine what possibilities those two super horses might produce," said Jackson, who owns a majority stake in Curlin.

The popular 4-year-old Rachel caused a stir last year when she won all eight of her races. Ridden by Calvin Borel, she beat fillies by 20 lengths in the Kentucky Oaks and 19 lengths in the Mother Goose Stakes before taking on the boys and winning the Preakness, Haskell Invitational and Woodward Stakes.

"The industry is going to miss her," said Hall of Fame jockey Mike Smith, who rides Rachel’s rival, Zenyatta.

Rachel had 13 wins in 19 starts and earned more than $3.4 million. In her last start, she finished second to Persistently in the Personal Ensign at Saratoga on Aug. 29 in what was her first race at 1 1/4 miles.

"As a 3-year-old, she set standards and records that no filly before her ever achieved, and I suspect it will be quite a while before a 3-year-old filly ever equals or surpasses her achievements," Jackson said.

Off the track, Jackson used her success to help raise money for various charitable causes including cancer research by auctioning off items related to Rachel.

1998 DERBY, PREAKNESS WINNER REAL QUIET, DIES

Real Quiet, the slightly built colt who in 1998 won the Kentucky Derby and Preakness and missed the Triple Crown by a nose, died at 15 on Monday.

The former champion 3-year-old died following a fall in his paddock, Penn Ridge Farms owner Mike Jester said. The horse broke his neck when his left shoulder hit the ground.

"It’s a pretty big blow for us," Jester said.