The 43-year-old jockey submitted a doctor's note indicating a foot injury suffered over the weekend was serious enough to warrant taking several days off.
"He came in this morning and had a doctor's note," steward Kim Sawyer said. "He's had X-rays, which were negative, I guess. He said the next step will be an MRI, which we were told may take place tomorrow."
Valenzuela took off his mounts on Sunday after the afternoon's third race citing a sore foot. Stewards were unaware of Valenzuela's location when he failed to show up for Wednesday's first race. He called them a short time later saying his agent should have already removed him from his mounts.
"He met with investigators this morning and was given a (drug) test," steward George Slender said. "He's good to go until next week where he will probably have to test again."
The oft-troubled Valenzuela currently rides under a strict conditional license that requires him to submit to regular drug testing, including urine and hair shaft/strand exams.