LOUISVILLE, Ky. -- Doing his own chores has Pat Day in jeopardy of missing his 21st consecutive ride in the Kentucky Derby.

The Hall of Fame jockey injured his lower back in a spill Sunday at Churchill Downs and further aggravated it Monday by hoisting a bag of yard debris into a dumpster. Day had shooting pain in his back and took off his mounts Tuesday, Wednesday and Thursday.

"Immediately, stupid was written on my forehead,'' he said. "You'd think after 49 years you'd get a little smarter. I should have been more careful.''

Day continued an aggressive regimen of deep muscle stimulation, ultrasound and alternating hot and cold treatments Thursday.

He hopes to fulfill his weekend commitments, including riding Ten Most Wanted, the 6-1 second choice in Saturday's Derby.