John Nash, assistant general manager of the Philadelphia 76ers, was named the NBA team's general manager yesterday by owner Harold Katz.

Nash, 39, who is also the team's business manager, replaces Pat Williams, who resigned last Thursday to become president and part owner of Pro Basketball Inc., an organization seeking an NBA expansion franchise for Orlando, Fla.

Jack Swope, the 76ers' marketing director, was named Nash's assistant.

Nash originally joined the 76ers in 1968 as group sales director and returned to the team in 1981 in his most recent post.

A source close to the team said Nash and Katz have been working on a potential trade.

Last week, the 76ers traded all-star center Moses Malone to the Washington Bullets and traded the team's No. 1 choice in the recently concluded draft to the Cleveland Cavaliers.

Through those deals, the 76ers acquired center Jeff Ruland, forward Cliff Robinson and center-forward Roy Hinson. BROADCASTING

ABC-TV will be "looking for relief" from the National Football League when it negotiates its contract for "Monday Night Football" in 1987 and, because of what it said were million-dollar losses, it may have to drop the game if it doesn't get concessions, a network spokesman said.

ABC Sports President Dennis Swanson said that, even though the ratings were up, the Monday night game lost millions of dollars for the network last year.

"When next year's negotiations come up, we will be looking for relief from that situation," said Irv Brodsky, the network's director of sports information. "If there is no relief, and there is no way out to run it economically, obviously we'll have to drop it. But that's a worst-case scenario."

"The problem is it's a five-year contract that was negotiated back in 1981-82, and the economic conditions are different today," Swanson told the New York Daily News. "We just can't afford to pay the kinds of dollars we're paying now." JURISPRUDENCE

John Flowers, a sixth-round draft choice of the NBA's Sacramento Kings out of Nevada-Las Vegas, was arrested on attempted rape, burglary and robbery charges in Las Vegas. Flowers was taken into custody by police shortly after midnight. Police said a resident of an apartment on South Arville Street telephoned authorities and said a man forced his way into her apartment and attempted to sexually assault her. She told police she kicked her assailant in the groin and escaped.

Flowers was booked into the Clark County Detention Center. He was held on $20,000 bail, plus an additional $830 bail for three outstanding traffic warrants. GOLF

Four players, including Britain's Sandy Lyle, shared the lead at 65 after the first round of the $245,000 Monte Carlo Open tournament. The other coleaders are Briton Chris Moody, Argentine Luis Carbonetti and American Bob Smith. Severiano Ballesteros of Spain was among six at 66. FOOTBALL

Miami Dolphins owner Joe Robbie has put up his team, its National Football League franchise rights and even the players' equipment as collateral for a loan, financial records reveal.

The amount and purpose of the loan are not specified in the public documents filed by CenTrust Savings Bank of Miami. Joe Abrell, a spokesmen for the Dolphins, also refused to reveal the amount and wouldn't say if the money will be used to help finance the $100 million Dolphins Stadium Robbie is building in northern Dade County. HIGH SCHOOLS

Pat Manson of Aurora (Colo.) Central High School has become only the third high school pole vaulter in the United States to clear 18 feet. Manson, 18, won the event Tuesday at an all-comers TAC meet in Lakewood, Colo., clearing 18 feet 1/8 inch.

Only Joe Dial and Brandon Richards previously cleared 18 feet as high schoolers. Dial's two jumps came early in the decade. Richards holds the high school record of 18-2, set in 1985. BOXING

A committee of the House of Representatives approved legislation creating a federal agency to oversee American boxing and establish uniform national safety standards for the sport.

The Education and Labor Committee approved by voice vote, without opposition, a bill sponsored by Rep. Pat Williams (D-Mont.) setting up the American Boxing Corporation, a quasi-public corporation modeled after the U.S. Olympic Committee. COLLEGES

Gabe Romano has been named sports information director at Catholic University. Romano, 26, most recently assistant to the publicity director for the National Old Timers Baseball Classic, is a former assistant public relations director for the Washington Federals (USFL) and was a sports information staffer at the University of Maryland after his graduation there in 1982. An Alexandria native, he was an assistant women's basketball coach at Maryland in 1984-85, then was head basketball coach at Stone Ridge School in Bethesda. MISCELLANEOUS

A committee of government, sports and business leaders has recommended that a 70,000-seat domed stadium be built for football and that the existing Atlanta-Fulton County Stadium be replaced by an open-air stadium for baseball by 1995.

Members of the committee said the cost of the new stadiums, whose primary tenants would be the National Football League Falcons and the National League Braves, could be $160 million and $60 million, respectively.