Mark McGwire (55 homers) missed a chance to gain on Sammy Sosa (59) in the home-run race yesterday, sitting out with an injured left groin muscle.

The Cardinals' first baseman left Monday night's game after 4 1/2 innings. He injured the groin compensating for a stiff back and may miss today's game as well.

"He's still got a little pinch in there," Manager Tony La Russa said. "If I had to bet a dollar, I'd say Friday" as the day he'll be back. The Cardinals are off Thursday.

WILLIAMS TAKES LEAVE: NL RBI leader Matt Williams has left the Diamondbacks to be with his family.

Diamondbacks Manager Buck Showalter said Williams told him about a serious illness in his family on Sunday, and caught a flight to Carson City, Nev., yesterday along with his children and his wife, actress Michelle Johnson.

Manager Buck Showalter said he did not know when the third baseman would return. "He's gone for as long as it takes him to feel comfortable about the situation," Showalter said.

CUBS' HILL GETS EXTENSION: The Cubs agreed to terms with OF Glenallen Hill on a one-year contract extension, the team said; the club retained an option for the 2001 season.

SURGERY FOR OSUNA: Reliever Antonio Osuna, who hasn't pitched for the Dodgers since May, is scheduled to undergo reconstructive surgery Thursday. Frank Jobe will perform the 90-minute operation, during which a ligament will be taken from Osuna's left wrist and placed in his pitching elbow. An MRI exam last month revealed a partial tear. Jobe, who also performed this landmark operation on Orel Hershiser and others, estimated it would be at least a year until Osuna can pitch in a major league game again.

METS ADD RUSCH: The Mets acquired LHP Glendon Rusch from the Royals for RHP Dan Murray. The Mets also acquired minor league P Justin Dunning from the Mariners to complete the June 18 trade that sent P Allen Watson to Seattle for P Mac Suzuki.