Twenty-one players must decide by midnight tonight whether to file for free agency but Bruce Hurst of the Boston Red Sox already has made his decision.

Hurst, who went 18-6 and helped the Boston win the American League East, was among 10 players to file for free agency Thursday, increasing the total to 73. Hurst made $900,000 in 1988 and his agent, Nick Lampros, is looking for a long-term contract.Also filing Thursday were pitcher Jesse Orosco and outfielder Mike Marshall of the World Series champion Los Angeles Dodgers. Los Angeles has six players who have filed for free agency. World Series hero Mickey Hatcher, who was eligible to file, agreed to a contract Thursday night with the Dodgers along with reliever Alejandro Pena.

General manager Fred Claire said earlier this week that he would not negotiate with his club's free agents after today's deadline, but might offer them salary arbitration. Clubs have until Dec. 7 to offer arbitration and players have until Dec. 19 to accept.

Also filing Thursday were pitcher Neil Allen and infielder Wayne Tolleson of the New York Yankees, pitcher Andy Hawkins of the San Diego Padres, catcher Jim Sundberg of the Texas Rangers, infielders Phil Garner of the San Francisco Giants and Graig Nettles of the Montreal Expos and outfielder Rick Leach of the Toronto Blue Jays.

Toronto announced Thursday that it would not exercise the option for 1989 in Leach's contract.

Frank Tanana, who could have been a free agent, Thursday agreed to a new contract with the Detroit Tigers for about $925,000, a cut from his $1.1 million salary.

Among those eligible to file today in the AL are pitcher Dennis Lamp of Boston, pitcher Dan Petry of California, pitcher Shane Rawley of Minnesota, catcher Don Slaught of the Yankees, pitcher Dave Steib of Toronto, and pitcher Rick Honeycutt and infielder Tony Phillips of Oakland.

Those eligible in the National League are catcher Ted Simmons of Atlanta, outfielder Jerry Mumphrey of the Chicago Cubs, first baseman Leon Durham of Cincinnati, third baseman Buddy Bell of Houston, outfielder Mookie Wilson of the New York Mets, outfielder Glenn Wilson of Pittsburgh, catcher Bob Brenly of San Francisco and pitchers Steve Bedrosian and Kent Tekulve and infielder Tommy Herr of Philadelphia.