The Alsab Stakes was not the private function Laurel fans anticipated yesterday between Stalker and Silent Generation. Each of the powerful favorites had the spotlight for a spell, until Will Lacy barged in and became the life of the party.

The 3-year-old colt needed the best performance of his 13-race career to get past Silent Generation (9 to 5) in the last sixteenth of a mile for a half-length victory, which gave jockey Joe Rocco a sweep of the weekend stakes races here. Will Lacy's biggest payday, $32,685, came one week after trainer Mert Bailes watched his top filly, Local Thriller, run off the track and into the stable area before a stakes race.

"I was scared to death," said Bailes, who rushed to the backstretch that day to find his fast filly unharmed, but wearing one less shoe.

With Laurel's racing surface fast and favoring inside speed, Stalker was made the 9-10 favorite in the five-horse Alsab. He had the quickness, the rail and the hottest trainer here (Ben Perkins Jr., seven for 12), but he didn't have the means.

He stayed a length in front of Silent Generation through a good half-mile of 45 2/5 seconds, but couldn't sustain himself into the stretch. Silent Generation pushed past him turning for home, and Will Lacy followed about two lengths behind the new leader. He caught Silent Generation near the half-furlong pole and went on to win the seven-furlong race in 1:23 2/5, paying $15.20 as the fourth choice.

Silent Generation had 1 1/2 lengths on third-place Joe's Lad. Loui Bomacino was fourth, Stalker last.

Will Lacy, who was in a $50,000 claiming race five weeks ago, produced somewhat of an upset when he beat older horses in an allowance race June 17. That convinced Bailes the colt was ready for the Alsab.

"I think you saw his potential today," Bailes said. "I don't think he can run any better." Rigione Suspended

After winning his first race of the meeting aboard Karnak On The Nile, apprentice Bobby McWhorter remarked Thursday how the 3-year-old ran much straighter than in his previous race. A report released yesterday by the stewards might help explain why: Karnak On The Nile tested positive for excessive phenylbutazone.

Trainer John Rigione waived his right to have a split sample tested and began a 15-day suspension yesterday. Karnak On The Nile's disqualification gave the $4,500 winner's purse to Prince Of Spades. Stakes Schedule Set

Pimlico, which released the stakes schedule for its meeting that begins July 26, officially marked the first Frank J. De Francis Memorial Dash for Aug. 18. Candidates for the $350,000 sprint -- to be televised by ABC -- include Safely Kept, Housebuster, Sunny Blossom and Beau Genius. . . .

Apprentice Mark Johnston led the country's jockeys in victories through the first six months of the year. Johnston won 214 races in Maryland through June 30, followed by Edgar Prado (166), Mario Pino (99), Marco Castaneda (98) and Joe Rocco (94). King Leatherbury, as expected, led trainers here with 80 victories, while Dale Capuano had 36, Fran Campitelli and Carlos Garcia 35 and Barclay Tagg 32. . . .

It took jockey Alberto Delgado one afternoon to match his victory total of the previous 13 days this meet. One of Delgado's three wins came astride Asoleada, who ended a 48-race Laurel-Pimlico winless streak for trainer Bill Wolfendale.