~ The filly has won her last four races.

NEW YORK -- It's a go for Rags to Riches.

The fabulous filly will run Saturday in the Belmont Stakes, where she will attempt to become the first of her sex in 102 years to win the final jewel of the Triple Crown.

Trainer Todd Pletcher took several days before deciding to give his Kentucky Oaks winner a chance to take on the boys in the 1 1/2-mile Belmont, the longest of the Triple Crown races.

"We're going in because we think we have a chance to win," Pletcher said Tuesday morning outside his barn at Belmont Park. "The filly is doing very well."

The addition of a filly in the Belmont spices up a race that will be run without Kentucky Derby winner Street Sense.

"It should make it interesting," Pletcher said. "I'll be as excited as anyone else."

Rags to Riches has won her last four starts, taking the Santa Anita Oaks before her impressive win in the Kentucky Oaks on May 4.

The decision is having a big effect on the Belmont field. At least one horse, Time Squared, has been pulled out of contention, and several jockey changes have been made.

John Velazquez, who was set to ride Slew's Tizzy in the Belmont, is Pletcher's No. 1 rider and now will be aboard Rags to Riches. Garrett Gomez, who has ridden Rags to Riches to her four victories, will stay aboard Hard Spun, replacing Mario Pino. Rafael Bejarano is the new rider for Slew's Tizzy.

Also, trainer Nick Zito may enter C P West, who finished fourth in the Preakness. The post position draw is today.

Rags to Riches looks to be a formidable foe for Preakness winner Curlin, the likely favorite for the Belmont.

"I would certainly identify Curlin as the horse for everyone to beat," Pletcher said. "If I was anybody else in the race, I wouldn't be excited that she was in there running against me."

Rags to Riches would be the first filly in eight years and 22nd ever to run in the Belmont. Silverbulletday finished seventh in 1999, and two fillies have won -- Tanya in 1905 and Ruthless in 1867.

Pletcher based his decision on several factors -- his filly is bred to run 1 1/2 miles and has been training well, and the defection of Street Sense has opened up the field.

The 3-year-old filly is a daughter of 1992 Belmont winner A.P. Indy and a half-sister to Jazil, last year's Belmont winner.

"Arguably, she has the best pedigree for this race any horse could ever have," Pletcher said.

Rags to Riches put in a five-furlong workout in 1 minute, 3.84 seconds at Belmont on Sunday, and Pletcher said, "She's in very good form."

The filly was purchased for $1.9 million by bloodstock adviser Demi O'Byrne at the 2005 Keeneland September yearling sale for owners Michael Tabor and Derrick Smith.

Pletcher, meanwhile, is 0-for-28 in Triple Crown races, including 0-for-5 in the Derby on May 5 and 0-for-2 in the Preakness on May 19.

Circular Quay, sixth in the Derby and fifth in the Preakness, also was under consideration but Pletcher said the colt will skip the Belmont and prepare for a summer campaign.

Others set for the Belmont include Imawildandcrazyguy, Tiago and Digger.