THESE BIG LEAGUE TRYOUTS ARE FOR ROOKIES INTERESTED IN BIG BUSINESS

"The letters almost always say, 'I've always loved baseball and would like a job in the game,' " says Bill Giles, president of the Phillies. "I get 500 letters like that every year, most from highly qualified people." So do Frank Cashen, executive vice-president and general manager of the Mets, and many other baseball executives. "In 1979, Lee MacPhail [president of the American League] got the commissioner's office to start a program to help bring some of the best of these people into the game," Cashen says.

Thus began the Executive Training Program. From an estimated 10,000 applications sent to team and league offices and the commissioner annually, the most promising prospects are picked to be interviewed by baseball officials across the country. After that, the six to eight top candidates are given one-hour interviews at the commissioner's office, and as many as three are hired for a year. Trainees usually work in the offices of both leagues and the commissioner, with the National Association of Professional Baseball Leagues, which oversees the minor leagues, and with a club that needs extra personnel. This year's finalists, chosen in early July, are Martin Conway of Warners, N.Y., John Cordova of Albuquerque and Wendy Selig, daughter of Milwaukee Brewer President Bud Selig. If the pattern holds, they all will eventually get full-time jobs in baseball. Here's a rundown on the past winners and where they're working:

Class of 1979: Stephanie Vardavas is manager of waivers and player records in the American League office; Drew Sheiman is the Orioles' promotion director.

Class of 1980: The White Sox hired both Ken Valdiserri, who's their assistant public relations director, and William Smith, who is the general manager at the Sox' farm team in Appleton, Wis.

Class of 1981: M. Scott Smith is an executive assistant with the White Sox, and Margaret Thomas free-lances for the Yankees' magazine.

Class of 1982: Dan O'Dowd, the lone winner, became a sales and marketing coordinator for the Orioles.