The course for Saturday's Vodafone (Epsom) Derby is listed as soft Friday night but with more rain possible, the course may become softer by post time, according to a track official.
"We have given out the overnight going as soft, but where we end up is very much dependent on the weather," said Andrew Cooper, director of racing at United Racecourses. "Showers are possible for tomorrow."
The track applied water to parts of the course Monday as a result of a warm, dry weekend, which left the home straight and one other area a bit too hard.
"The decision to water these limited areas was also made at 7 a.m. on Monday morning, taking account of the weather forecast for the week ahead as it was at that time," said Cooper. "As a result, the course on Tuesday evening walked consistently on the faster side of good ground, which had been the intended result of the limited watering that was done. Showers, albeit light ones, were always a possibility within the weather forecast but it wasn't until Monday evening that any suggestion was given as to the possible intensity of Wednesday's rain."
Hawk King and High Chaparral head a field of 12 going into the race and have dominated betting for many weeks. No colt trained outside Britain and Ireland made this year's field.
Hawk Wing must defy the Derby's long-established curse on stall 12, the widest berth away from the inside rail, if he is to win the 1 1/2-mile race. No Derby runner has won, or been placed, from that start position since 1984.
Hawk Wing is bidding to become the first horse since Grundy in 1975 to follow a second place in the 2000 Guineas with victory in the Derby.
In last month's Guineas, he finished a neck behind stable-companion Rock Of Gibraltar after being drawn on the unfavored stands' side.
He produced a stunning burst of speed in the final furlong to almost win. Although he has wonderful acceleration, doubts remain over whether he will be able to stay the mile-and-a-half.
If he is able to conserve his powerful finishing burst until the final furlong, trainer O'Brien has no doubt that he has a realistic chance.
"Hawk Wing has loads of speed and plenty of class and quickens well," said O'Brien. "He has such pace. He'll be taking his time in the race. "If he stays, he stays, and if he doesn't then he doesn't. That's how he'll be ridden."
Godolphin has entered Convergent Dante Stakes winner Moon Ballad, along with Naheef. Frankie Dettori will be aboard Naheef as the Italian-born jockey seeks his first Derby victory.
Predominate Stakes winner Coshocton, trained by Michael Jarvis, is also among the declarations. Mark Johnston has dual hopes in Bandari and Fight Your Corner, who were both supplemented for the race at a cost of £90,000 pounds ($131,000) each this week.
Marcus Tregoning has entered Tholjanah, while Terry Mills has Where Or When and outsider Frankies Dream in the lineup. Andy Turnell has Jelani.
Where or When will start from the luckiest stall of all, number ten. Since 1984, six winners have come from that start position, including Galilelo, Shahrastani, Reference Point and Quest For Fame.
British bookmaker Coral has eased Hawk Wing to 13/8 from 6/4, with High Chaparral trimmed to 2/1 from 9/4.
"This rain will not help Hawk Wing's chances of staying the Derby trip, and if it continues High Chaparral may well start favorite for Saturday's race," Coral spokesman Simon Clare said.
Rival bookie William Hill, who also has the big two at those prices, reported a bet of 10,000 pounds (dlrs 14,600) at 6-1 on Bandari.
English Derby betting:
Coral: 13-8 Hawk Wing (from 6-4), 2-1 High Chaparral (from 9-4), 9-2 Bandari, 15-2 Naheef, 10-1 Fight Your Corner, 16-1 Moon Ballad, 20-1 Coshocton, 25-1 Tholjanah, 33-1 Where Or When, Louisville, 50-1 Frankies Dream, 80-1 Jelani.
William Hill: 6-4 Hawk Wing (from 11-8), 2-1 High Chaparral (from 9-4), 5-1 Bandari (from 6), 7-1 Naheef, 10-1 Fight Your Corner, 16-1 Moon Ballad, 25-1 Coshocton, Tholjanah, 66-1 Louisville (from 50), 100-1 Where Or When, 150-1 Frankies Dream, Jelani.
Ladbrokes: 6-4 Hawk Wing, 9-4 High Chaparral, 5-1 Bandari, 8-1 Naheef, 10-1 Fight Your Corner, 16-1 Moon Ballad, 25-1 Coshocton, 25-1 Tholjanah, 40-1 Louisville, 50-1 Where Or When, 66-1 Frankies Dream, 100-1 Jelani.