Northern Wolf, possibly the best thoroughbred sprinter in Maryland, was injured Tuesday, a day he produced a blistering five-furlong workout. Now instead of a chance at the Breeders' Cup Sprint, he faces retirement.

The 4-year-old colt chipped a sesamoid bone in his left foreleg at Belmont Park, where he ran five furlongs in 56 3/5 seconds in preparation for the $1 million Sprint on Oct. 27. The workout was so swift it bettered the track racing record that has stood four years, :56 4/5.

Trainer Hank Allen, who had gone to New York to observe the run, defended exercise rider Mike Kummer's allowing the colt to work so briskly. Northern Wolf has produced brilliant workouts throughout his career.

"How do you determine what is too fast?" Allen asked. "Mike doesn't use a stick and doesn't ride him hard. We let {Northern Wolf} do what he wants to do. That's been the manner that we've worked this horse for some time. We didn't ask him specifically to go out there and have a blistering work."

Northern Wolf galloped out six furlongs that morning in 1:09 2/5, two seconds faster than Go For Wand, the country's premier filly.

Allen said he watched Northern Wolf walk off the track with no difficulty, then hurried to catch a plane home. His associates later feared something was amiss with the grayish colt, and an X-ray revealed a chip on the lower part of the leg.

Allen said he was told the horse "is not lame, and he's not limping around." He said he will ship Northern Wolf back to Bowie Race Course this weekend if the colt is up to it.

Howard Hoffman, a District resident who owns and bred Northern Wolf with fellow psychiatrists John Meeks of the District and Allen Cahill of Irving, Tex., said his group received "six to eight serious inquiries" from breeders seeking Northern Wolf's stallion services after the colt won the $350,000 Frank De Francis Memorial Dash in a Pimlico-record 1:09 for six furlongs Aug. 18. Two months earlier, Northern Wolf had set a six-furlong mark at Laurel of 1:08 1/5.

"We're going to be exploring those inquiries," Hoffman said. "The best opportunity for him to get a full book to good mares probably is in Maryland, where most people know him. We also want to be around him and watch his offspring. We had planned on standing him at stud; unfortunately, this means we're going to stand him a year earlier."

By Wolf Power -- a onetime star in South Africa -- out of the mare Glenorthern, Northern Wolf won seven of 20 starts and earned $461,107. He was having his finest year in 1990 with three victories, two track records and $282,153 accumulated in eight starts. The Breeders' Cup Sprint was to have been Northern Wolf's richest race.

"We know in Maryland that he's something special, and we were looking forward to letting the country see that he was something special," Hoffman said. "You realize what a heartbreaking sport it is: A horse who has all the potential in the world -- and in an instant it's all gone." Leatherbury Appeals

King Leatherbury has appealed his 15-day suspension for a phenylbutazone violation, alleging the medication overage resulted from "some kind of sabotage" to his horse, Wait For The Lady.

The Maryland Racing Commission yesterday received, and is likely to approve, a request by Leatherbury for a stay of suspension pending a hearing, assistant director Mike Hopkins said. The suspension was to begin Monday.

Leatherbury, whose 4,700 victories are third most in thoroughbred racing history, said Wait For The Lady had not trained on phenylbutazone, an anti-inflammatory medication, before her tainted victory Sept. 15. A postrace blood test showed the filly had more than three times the allowable level of Bute.

In addition to Leatherbury, stewards Tuesday set down trainers Deborah Blankenship and Georgia Andreadakis 15 days; each had a horse test positive. Blankenship's Jacamar had an overage of Bute in her 17-length triumph Sept. 14 at Pimlico; it was one of the largest margins of victory at a Maryland thoroughbred track this year. Andreadakis's Storm Session tested positive for methocarbamol, a skeletal muscle relaxant, after a third-place finish at Laurel this month. . . .

Fourteen European horses arrived at Laurel without incident yesterday for this weekend's International Turf Festival. The group did not include Lady Winner, who will bypass Sunday's $750,000 Budweiser International in favor of the $1 million Breeders' Cup Mile six days later.