NEW YORK — Rick Dutrow Jr. says he's concerned but confident Big Brown will be in top form for his Triple Crown attempt in the Belmont Stakes in less than two weeks.

The trainer of the unbeaten Kentucky Derby and Preakness revealed yesterday that his unbeaten colt has a slight crack on his left front hoof. He quickly added the injury is so minor it will be treated by hoof specialist Ian McKinlay in the next few days and Big Brown could return to training as early as Thursday.

"It scares us when something like this happens, but this has nothing to do with his ability to finish what he started," Dutrow said at a news conference outside barn 2 at Belmont Park. "Ian is assuring me and it's going to go down like clockwork. And he's still going to run the same race."

Maybe.

When it comes to Triple Crowns, only 11 3-year-olds have been able to sweep the Derby, Preakness and Belmont, with 18 others winning the first two legs but failing in the 1 1/2-mile Belmont.

Two others, Burgoo King in 1932 and Bold Venture in 1936 won the Derby and Preakness but didn't even make the Belmont because of injuries, according to most accounts.

Can the same fate await Big Brown, who has won all five of his races by a combined 39 lengths?

Dutrow and McKinlay doubt it, at least they did yesterday. They said the injury was detected Friday and Big Brown has missed two days of training and will miss at least three more.

"We're all concerned because there's a big race coming up," Dutrow said. "But Ian has us pretty well relaxed. He's telling me it's nothing and he'll be fine in a few days."

On Monday, McKinlay will treat Big Brown for the five-eighths of an inch-long quarter crack on the inside of his left heel.

"This is a very, very minor crack," McKinlay said. "We will put a set of wires in, stitch it up and then patch it."

Dutrow is thankful there's three weeks between the Preakness and Belmont as opposed to two weeks between the Derby and the Belmont on June 7.

"If it was two weeks we would be nervous, but this way I'm as cool as we can be," Dutrow said. "It's bad that this happened, but it's good that it happened at this time."

McKinlay has repaired injuries much more severe before big races, allowing Touch Gold to fight off a leg injury from the 1997 Preakness and go on to win the Belmont and spoil Silver Charm's Triple try.

Best-case scenario, he says, could allow Big Brown to return to the track Thursday.

"The worst case is he doesn't make the race," Dutrow said. "The horse is in great shape. He doesn't know anything is wrong with him. When you touch it and put pressure on it, he's going to give. But the worst possible thing that could happen is he doesn't make the race, and that will only hurt human beings. Not him. He's laying back, not worried about anything."

Dutrow said Big Brown continues to be taken for walks inside his barn twice a day, and is feeling no pain.

"If the race was today, yesterday or tomorrow, it would not be an issue," he said.

A quarter crack is a vertical crack in the hoof wall between the toe and heel of the hoof, usually extending into the coronary band, where the hoof meets the skin of the leg.

For the most part, the injury is fairly common and not considered serious. Healing time can range from a few days to a few months, depending on the severity of the crack.

Foot woes are nothing new to Big Brown. When he first arrived at Dutrow's barn in Aqueduct late last year, he sustained an abscess in the sole of his left front foot, which caused a wall separation and sidelined him for 45 days.

In January, he suffered the same injury to his right front foot and missed another 45 days. Those injuries were called quarter cracks, even by Dutrow. But McKinlay noted there's a big difference.

"A quarter crack is just a split, literally, in the wall and it will start at the hairline and travel down but never reach the sole," he said. "A wall separating is the exact opposite. It starts from the sole and runs to the top. And it's very painful.

"As far as this crack goes, it's very minor."

Dutrow first noticed something was amiss when one of his grooms called him over on Friday after a morning gallop. Dutrow didn't want to take any chances so he called McKinlay.

"I was hoping maybe he banged it on a side of the wall. He's getting pretty aggressive when he walks in the afternoon, and really bossing people around," he said, "But I knew in my heart he was developing something that I didn't want to see."

The hoof was treated with a combination of iodine and alcohol Saturday.

Dutrow is looking ahead.

"I am sure he will be 100 percent, yes," Dutrow said. "If we get to breeze him (next) Tuesday or even Wednesday, we can live with that. Monday would be great as long as Ian can get it done the right way.

"Now if something else happens, then we're going to be in trouble."