Sugar Ray Leonard climbs through the ropes again for Howie Cosell and the ABC camera plus a live Las Vegas audience (Dunes) on Saturday, April 21, and the obstacle in the path of his 21st straight pro victory could be formidable:

Adolfo Viruet of New York's fighting Viruet brothers.

The Palmer Park welterweight will have to go some to log his fifth straight Kayo. Two-time N.Y. Golden Gloves champ Viruet has won 17 of 20 for pay, recently defeating Monroe Brooks in a 12-rounder for the North American junior welter title at Madison Square Garden . . .

ABC Sports is out too with its NCAA early season football schedule: Wept. 8, Alabama's national chmpions versus soon-to-be-ACC Georgia Tech (here's hoping new Yellow Jacket assistant Norm Van Brocklin, after his recent brain surgery, is part of it)...And Sept. 15, regional 'casts includeing Maryland at Clemson starring Charlie (Ironjaw) Bauman of Gator Bowl fame. Wonderful for the Terps to get early exposure for a change; no doubt attributable to the 28-24 thriller they lost the the Tigers in Byrd Stadium for 1978 ACC laurels and the celebrity of Clemson's flollow-up Hayes-ing in Jacksonville.

A tsk-tsk though, Maryland-Clemsoin conflicts with heck of a featured ABC-TV regional that day-Notre Dame at Michigan.

Does Sept. 8 opening mean retrenchment, thank goodness, from the seemingly inexorable march toward college football in August? Not necessarily; the network is said to be involved in a projected tieup with Giants Stadium in Jersey for an annual pre-Labor Day biggie.

The St. Louis Cardinal visit Pittsburgh on Thursday, and seeing as how these are the baseball Card, Manager Ken Boyer says he will lodge a protest if Dave Parker wears his football-style helmet against 'em.

"He intimidates you wearing that mask," said Boyer of the 6-5, 230-pound Parker. "Heck, he scarews you without it."

Parker began wearing the mask after suffering a broken cheekbnone in a collision with Met catcher John Stearns, who tagged him for a game-saving out. Parker had the ,mask on Saturday when he crashed into Montreal catcher Gary Carter and scored the winning run as Carter dropped the ball. Parker was hurt nine months ago...

A1 McGuire (at the Hoya banquet April 19) will have to fall in line to honor John Thompson's Georgetown 24-5 basketball heroes. D.C. City Council has proclaimed today Georgetown University Basketball Day in the District. Coach and squad will be at Council chambers, District Building, 7:30p.m., for ceremonies...George Mason keeps moving up on the local sports scene, its intramural aces beating Georgetown, 55-48, Sunday (after hurdling PGCC, Maryland, AU) to annex the D.C. Extramural basketball championship to GMU's D.C. Extramural touch football title ...Glenn Haris, 31, tells Howard U. buddies he's caught that rainbow and made the team, the Class AAA Panama Bankers, for his first shot at catching in organized baseball....

The bill on Mu Tieh-Chu, the basketball Great Wall of China, has shriveled from 7 feet 9 (for his preseason joust with the Hoyas) to 7-2, but he and his cohorts evidently are just as tough as when they trimmed GU, 75-69, in Cap Centre Nov. 16. Mu led China's Aug. 1 Army team to a 104-96 upset over a U.S.all-star collelge tema before 18,000 last night in Peking.

Spingarn's 6-11/2leaper, Diego McCoy, meanwhile has opted for West Virginia and 6-8 Bob Donohoe of St. John's for James Madison.

In the UCLA fold: Verbum Dei H.S., one of sunny Cal's most desperately recruited. CAPTION: Picture, Car driven by Patrick Tambay goes atop Niki Lauda's racer during Long Beach Grand Prix. Neither was hurt. AP