ARCADIA, Calif. -- Patrick Valenzuela, the top jockey in Southern California last year, hired former jockey Corey Black as his agent Thursday morning and then took off his mounts after twisting his ankle when he slipped on a mat as he left his house.

In a telephone interview, Valenzuela said he planned to return to riding at Santa Anita on Friday, when he was booked on three mounts. Saturday, he has eight mounts, including all four of the Sunshine Millions stakes here.

"I was running out of the house, and I tripped over the rain mat," he said. "I slipped and twisted it bad. Hopefully, I'll be back to riding tomorrow."

Valenzuela won riding titles at all five of the major race meetings in Southern California last year, his second year of a comeback following a two-year absence for substance abuse problems. Valenzuela, 40, holds a conditional license that subjects him to random drug testing. His career has been plagued with substance abuse problems.

The stewards ordered him to be tested after he took off his mounts. As of mid-afternoon Thursday, he had not arrived to be tested at Santa Anita, according to track stewards.

Valenzuela acknowledged that his absence Thursday, combined with his absence from workouts Tuesday through Thursday mornings, has led to backstretch talk that he is having personal problems.

"A couple of people mentioned that to me," he said. "I was coming out to workouts during Oak Tree and Hollywood Park. I'm probably not working as hard in the mornings as I did, but my riding is 110 percent."

Through Monday, Valenzuela was seventh in the standings with 10 winners, 12 behind top rider Alex Solis. Valenzuela had 13 mounts in the first two weeks of the meeting while serving suspensions from 2003. He was allowed to ride only some stakes that are exempt from routine suspensions. During one five-day period in early January, he was not allowed to ride any races.

Valenzuela fired agent Nick Cosato on Monday, citing the desire to have an agent who represented only one rider. Cosato also books mounts for Corey Nakatani.

Earlier in the week, Valenzuela spoke with agent Bob Meldahl about possible employment, but Meldahl declined the offer. Meldahl currently books mounts for Mike Smith, who is third in the Santa Anita standings.

Black said "he threw his hat in the ring" Tuesday and took the job with Valenzuela on Thursday. "Pat called and said, 'Do you want to go to work?' " Black said.

Black said he would continue with his color commentary position on the TVG racing network, which he does five afternoons a week.

Black retired from riding in 2000 and worked as an agent in the following months for Gary Stevens and Brice Blanc. In recent years, he has worked primarily on TVG but has continued to exercise horses for major stables such as Neil Drysdale and Richard Mandella. He was working as an exercise rider at Santa Anita on Thursday.

Black said he made it a point to tell Valenzuela that he would not be able to spend considerable time at Santa Anita in the afternoons because of the TVG commitment. TVG does not present Santa Anita's races, which are shown on the rival Horse Racing TV network.

Black said the arrangement with Valenzuela would be easier for him at Hollywood Park, because Hollywood's races are shown on TVG and Black would be at the track.

Krone targets early-February return
Jockey Julie Krone said Thursday that she hopes to receive doctor's permission next week to resume riding in early February.

Krone suffered fractures to two ribs and soft tissue damage in her upper chest in a two-horse spill at Hollywood Park on Dec. 12. At the time of the injury, she was the leading rider at that meeting.

"From the way it's looking from my last visit to now, the healing process is going really well, especially the soft tissue," Krone said. "I'm ready to get back."

Last year, Krone missed more than four months with a back injury when she was unseated after the start of a race at Santa Anita on March 8. She returned to ride at Del Mar, where she finished second in the jockeys' standings to Valenzuela and won the meeting's richest race, the $980,000 Pacific Classic, aboard Candy Ride.

Last fall, Krone won her first Breeders' Cup race when Halfbridled won the Juvenile Fillies.

Krone has said she wants to be back to riding in advance of Halfbridled's scheduled 3-year-old debut in the $250,000 Las Virgenes Stakes at Santa Anita on Feb. 15.