Kentucky Derby favorite Mister Frisky, unable to eat because of a tennis ball-sized lump in his throat, was being treated with antibiotics yesterday to combat a life-threatening condition, veterinarians said.

"It's a situation where there won't be any rapid improvement or decline, hopefully," said Scott E. Palmer, surgeon at the New Jersey Equine Clinic in Clarksburg, N.J.

Mister Frisky, who had won his first 16 lifetime starts, finished eighth in the Derby, then ran third in the Preakness. His condition probably affected his performance, and he has lost 100 pounds since it was diagnosed, Belmont Park veterinarian Robert Fritz said.

"The prognosis is guarded, and it remains guarded until further notice," Fritz said. "This is a very complex condition. It is life-threatening. The horse remains in serious condition."

Shipped from Pimlico to Belmont Park a couple of days after the May 19 Preakness, Mister Frisky developed a fever before the abscess was discovered. Fritz said Friday the abscess "grew to the size of a grapefruit. It is down to about the size of a tennis ball now."

There has been speculation that the infection might have been bothering Mister Frisky before the Kentucky Derby.

"I don't know about that," trainer Laz Barrera told the Los Angeles Times Friday. "He looked so good in Kentucky. We checked his temperature every day, and there was never any fever. Anybody who saw him in Kentucky can't believe he's sick now, because he looked so good there."

Pimlico: In Baltimore, Highland Devotion saved ground along the rail before rallying in the stretch for a 1 1/4-length victory over Social Retiree in the $58,450 Broad Brush Stakes. The even-money favorite in the field of 12 3-year-olds ran the

1 1/16 miles in 1:43 4/5 over a firm turf course.

Jockey Edgar Prado notched his second of three winners on the program to earn a $35,070 winner's prize for the Gold'N'Oats Stable.

Social Retiree, who led much of the way, finished another 1 1/4 lengths in front of J.R.'s Horizon, who was making his first start since the Preakness.

"I was waiting for room," said Prado, who had his mount as far back as eighth with a half-mile remaining. "There was plenty of time at the half-mile pole. I worried the last quarter if I couldn't find a hole I'd have to swing wide, but a hole opened."

Highland Devotion had won an allowance race at Gulfstream Park in his grass debut and then came to Pimlico, where he finished a nose behind Baron de Vaux in the Woodlawn Stakes May 6.

"It looks like he's taking a nice fondness for the turf," said Steve Klesaris, who saddled the colt for his brother, trainer Robert Klesaris. "We plan on picking our spots from here."

Belmont Park: Yankee Affair reestablished his momentum after entering the stretch, ran down the leader in the final yards and responded gamely to hold off Hodges Bay in winning the $117,600 Red Smith Handicap in Elmont, N.Y.

Yankee Affair, the highweight at 122 pounds, ran the 1 1/4 miles in 2:00 1/5 on the turf. Jose Santos was in the saddle for Yankee Affair's second victory in four starts this year.

Hodges Bay closed strongly to finish second in the seven-horse field, a head in front of Phantom Breeze.