LOUISVILLE, Ky. --- It's still a waiting game for Rachel Alexandra and jockey Calvin Borel to see whether one or both will be in the Belmont Stakes.

Preakness winner Rachel Alexandra worked a half-mile at Churchill Downs on Monday, but the filly's owner said it could be another week before he decides whether to enter her in the final leg of the Triple Crown on June 6.

Jess Jackson said Rachel Alexandra is "progressing well" and will work again next week before a decision is made on the Belmont.

Jackson and Harold McCormick bought Rachel Alexandra after she won the Kentucky Oaks by 20 1/4 lengths May 1. On May 16, she became the first filly in 85 years to win the Preakness, with Borel guiding her to a one-length victory over Kentucky Derby winner Mine That Bird. Mike Smith replaced Borel aboard Mine That Bird in the Preakness.

"She's recovering nicely and I think, for the time that's elapsed, only nine days, she's right on -- but we can't make a decision until we know," said Jackson, who owns Stonestreet Stable. "My concern is her attitude. She thinks she can run through a brick wall, so her attitude has to be monitored. If anything, we have to hold her back a little bit because she's so eager to run."

Borel is waiting on a decision about the filly's status before he decides who he's going to ride in the 1 1/2-mile Belmont.

Rachel Alexandra worked the half-mile in 50.20 seconds over a sloppy track under exercise rider Dominic Terry. Mine That Bird worked the same distance in 51 seconds under Borel.

If Rachel Alexandra doesn't run in the Belmont, Jackson said the Mother Goose Stakes for fillies at Belmont Park on June 27 is an option.

With the no-decision, Mine That Bird trainer Chip Woolley gave Borel more time to decide which horse he'll ride in the Belmont. Woolley had set a Monday deadline for the jockey.

"He won me a Derby; he deserves the time it takes for him to make the conscious, right decision," Woolley said.

No filly has won two-thirds of the Triple Crown, and no jockey has ever won the Triple Crown by riding different horses.

If Borel chooses Mine That Bird, Jackson will go with Robby Albarado if the filly runs in the Belmont. Albarado is one of the top riders used by Steve Asmussen, who took over as the filly's trainer after the horse was sold.

Jackson said Rachel Alexandra will give him a sign whether or not the Belmont is next.

"We have to monitor her and make sure that we preserve her because she's so special," he said.