Rookie Walt Weiss, the ninth-place hitter in a lineup of sluggers, singled home the tie-breaking run in the ninth inning last night and the Oakland Athletics beat the Boston Red Sox, 4-3, for a commanding 2-0 lead in the American League playoffs.

The Athletics headed home, where they swept all six games from Boston this season and have won 14 of the last 15. Game three is tomorrow night with Oakland's Bob Welch facing Mike Boddicker.

Jose Canseco, who led the majors with 42 home runs and 124 RBI, homered for the second straight game and Mark McGwire hit an RBI single in the seventh for a 3-2 lead before Rich Gedman's home run in the bottom half of the inning tied it.

But while Oakland's Bash Brothers brought the Athletics back against Roger Clemens, it was the bottom part of the order that won it. Ron Hassey singled with one out against Red Sox relief ace Lee Smith and took third on Tony Phillips' two-out single. That brought up Weiss, a .389 hitter against Boston this year, and he escaped an 0-2 hole against the fast-balling Smith and lined a single just in front of diving center fielder Ellis Burks.

Dennis Lckersley, who led the majors with 45 saves, got his second save of the series. Gene Nelson went one inning for the victory while Smith, who got out of a first-and-third jam in the eighth by retiring Canseco and Dave Parker on fly balls, took the loss.

Clemens heated up from the start on a night when frost warnings were posted in Boston and the Bruins opened the hockey season. Clemens retired the first nine batters, including four in a row on strikeouts.

Oakland's first hit wasn't much to brag about. Luis Polonia opened the fourth with a dribbler to the right side of the mound that Clemens fielded cleanly but then threw wide of first baseman Todd Benzinger. Polonia was credited with a single and was given second on Clemens' error.

After Henderson struck out, Polonia tried to steal third with Canseco at the plate and was thrown out. Gedman, who threw out 39 percent of potential base stealers this year--slightly below the league average--made a strong throw, and Canseco then lined out to end the inning.

Clemens struck out the side in the sixth around a double by Tony Phillips. That gave Clemens seven strikeouts without a walk.

Davis wasn't as overpowering as Clemens, but just as effective. He did not allow a hit until Benzinger opened the fifth with a hard one-hopper that hit Davis in the right knee. The ball bounced away for a single.

"You knew it would be a dogfight coming into Fenway Park and facing Bruce Hurst and Roger Clemens," Weiss said. "But we can't let up now."

"We were up for this game and the way Roger was throwing the ball, I just knew he was going to shut them out," Boston manager Joe Morgan said. "I thought we were a shoo-in."