Mary Russ, the Floridian who has shown her (mounts') heels on the sunshine circuit, will pack her tack after a final ride on Joanie's Chief at Gulfstream on Saturday and give the New York tracks maybe their biggest little jockey sensation since Steve Cauthen. She owns the Tropical-at-Calder riding title. She aims to start Tuesday at Aqueduct.

"The timing is perfect," says Roger Laurin, aboard whose Lord Darnley she won the Widener and Gulfstream Handicaps, pioneer accomplishments for a woman jockey (she brought Laurin's Our Escapade, 80 to 1, in third in the $250,000 Florida Derby). Russ' agent, Bobby Vandel, echoes: "She'll get to ride more good horses and she'll make four times the money . . . She's good enough to make it" . . .

And mind the missteps. A widow and two children in Panama grieve for Amado Credidio Jr., the jockey spilled and trampled at Aqueduct March 29 . . .

The daddy of marathons is off to a jostling start even before the thousands mass at Hopkinton, Mass., April 19. Prudential, major benefactor for 16 years, says this is its last: "The Boston Marathon, after 86 years, will change its 'noncommercial' character, and as such, it will no longer serve the goals and objectives of the Prudential's public service purpose." This after Will Cloney, Boston A.A. president and race director, corralled new sponsors including Seiko, Dodge and Bristol-Myers; spoke of "necessity of putting the marathon on a more professional basis (including major additions to staff)--and pressed Hopkinton's town board of selectmen for Sunday dates (ah, TV) in future, instead of traditional Monday, Patriots Day . . .

Masters week, and here's NFL Alumni's Redskin chapter, led by Carlton Kammerer and Andy Davis, swinging out after entries in its third annual charity golf (now, plus tennis) outing May 3 at Indian Spring. "Caring for Kids"--special emphasis on Special Olympics among good causes. Winning team qualifies to vie with those from 25 other NFL Alumni tournaments--chance to win it all as Chuck Hinton and friends did last year in the "Super Bowl of Golf" in October at Hilton Head.

Baseball week, and Scott McGregor to speak for Oriole players as a delegation of Baltimore's finest, led by bosses Williams, Peters and Weaver, lunches at Touchdown Club here today . . . Grandstand Managers and Alexandria Baseball Boosters sup at Old Town Ramada tonight to welcome their Dukes on eve of Carolina League opening . . .

Event Friday: U.S.-China volleyball, national teams fresh from Caesars Palace, Las Vegas, and Denver, serve it at GWU's Smith Center, 7:30. U.S. won first two tests, in California; lost in Nevada.

AL umpire Larry Barnett got more than bargained for, with the umps' pay raise, on season opening. Ninth inning of Angels-A's in Oakland, a foul tip by Jim Spencer broke Barnett's mask, jagged edge inflicting a three-stitch head cut . . . Tough occupation. While Denver U. Coach Jack Rose argued and drew thumb by ump Steve Clark Tuesday as DU trailed Metro State, Rose's assistant, Glen Schwab, threw a stone from afar. Lit at Clark's feet, bounced and hit his face (no serious damage). It cost DU a forfeit, right there--and Schwab his job, yesterday . . .

Jerry Sherk has retired after 12 NFL years: a good defensive tackle in a 1981 comeback from injuries; a great one until 1979 staph infection from a knee scrape on Philadelphia's artificial turf . . . Second NFL Cardinal in a week drug-busted: a raid by West Alabama narcotics squadders in Tuscaloosa ensnared LB E.J. Junior--released on $1,500 bond, charged with possessing cocaine (felony) and marijuana (misdemeanor) . . .

Yale's basketball coach, Ray Carazo, quits, for parts unknown, after 13-13 year.

A. Anchor on Navy's 400 relay: tailback Eddie Meyers . . . Q. Homer hitter for Denver U. in game forfeited to Metro State: a player whose dad, same name (initials L.A.) hit 83 HR in the majors. ???