Forward John Williams, who led Louisiana State to the Final Four this year, announced yesterday he is giving up two years of eligibility to enter the National Basketball Association draft.

"I'm doing today one of the most painful things I ever did in my life," he said at a news conference. "I am resigning from LSU to pursue a pro basketball career."

Williams, a 6-foot-8 sophomore, said, "I am doing this for one reason and one reason only: I have to support my mother and grandmother."

Twice late in the season, Williams had said he would play his full four years at LSU and then try to make the U.S. Olympic team. . . .

College player of the year Walter Berry appears to have firmed up his decision to play his senior year for St. John's. "I thought about it turning pro by the May 3 deadline when I thought there was a chance I would be the No. 1 pick in the draft June 17 ," Berry told the New York Post. "But, it seems they're planning on picking a center first." . . .

Xavier McDaniel, who had 17.1 points and eight rebounds a game for the Seattle SuperSonics, is the only unanimous pick for the NBA's all-rookie team.

McDaniel drew 22 votes in balloting by the 23 head coaches (no voting for one's own players), one more than Patrick Ewing, the New York Knicks center who averaged 20 points and nine rebounds but was limited by injuries to 50 games. Rest of the first team: Karl Malone of Utah, 17 votes; Joe Dumars of Detroit, 15, and Charles Oakley of Chicago, 13.

Manute Bol was one of seven others receiving votes.