Mendelssohn, second choice on the Kentucky Derby morning-line, could be seen through screening at the Churchill Downs quarantine barn Wednesday morning walking the shed row under tack and rider.

Mendelssohn, the 18 1/2-length winner of the United Arab Emirates Derby on March 31, arrived at Churchill from trainer Aidan O'Brien's base in Ireland on Monday night. The colt remained under a standard U.S. Department of Agriculture quarantine during training hours Wednesday but is scheduled to come out of quarantine Wednesday afternoon and have the first of two morning training sessions at Churchill on Thursday, when O'Brien and jockey Ryan Moore are scheduled to arrive here.