Undated (AP) _ Outfielder Eric Davis, out since May 3 with a hamstring injury, has been activated from the disabled list. The Reds also announced Thursday that right- handed pitcher Jeff Sellers would likely be lost for the season as a result of arthroscopic surgery on his right shoulder and that infielder-outfielder Skeeter Barnes had been assigned outright to Nashville, the Reds' AAA affiliate. Davis has a .238 batting average, with six home runs and 18 RBIs this season. Houston

The Astros lost 4-3 to St. Louis in 10 innings Thursday, snapping a five game-winning streak. ... Bob Knepper's 91 victories are the most by an Houston left-hander ever. Knepper has allowed only one home run to a left-handed batter (Darryl Strawberry since the start of the 1988 season. Los Angeles

John Shelby singled in the second and doubled in fourth innings Thursday night, giving him six hits in 15 career at-bats against Dwight Gooden of the New York Mets. . . . Tim Leary is winless in five appearances against the New York Mets, the club he began with. . . . Dave Anderson was surrounded Thursday by reporters seeking details of his collision Wednesday with Keith Hernandez. ''How come you guys only interview me after something bad happens,'' he joked. ''The last time was a couple of years ago when I struck out four times against Dwight Gooden. New York Mets

Keith Hernandez, a lifetime .300 hitter in 15 major league seasons and one of the game's best fielding first basemen, will be lost to the Mets for about eight weeks because of a fractured right kneecap. Hernandez, 35, was injured Wednesday night when he collided with Los Angeles shortstop Dave Anderson while breaking up a double play during the fifth inning of the Mets' 4-3, 10- inning loss. ... Dave Magadan's triple off the Dodgers' Tim Leary Thursday night was his third in 569 major-league at-bats. ... Ron Darling was honored by the National Fathers Committee as a ''Father of the Year'' on Thursday along with New York radio personality Bruce Morrow, television personalities Ernie Anastos and Len Berman and Vice President Quayle. Pittsburgh

The Pirates on Thursday sold the contract of minor-league infielder Orestes Destrade to the Seibu Lions of the Pacific League in Japan. The sale is pending the approval of the commissioners' offices in both the U.S. and Japan. Destrade, 27, was acquired from the New York Yankees on March 30, 1988, in exchange for pitcher Hipolito Pena. He appeared in 36 games with Pittsburgh last season, hitting .149 with one homerun and three runs batted in. In 32 games this season with the Buffalo Bisons, the Pirates' AAA affiliate, Destrade was hitting .232 with one homerun and 17 RBIs. St. Louis

The Cardinals placed right-hander Ted Power on the 21-day disabled list with a pulled rib-cage muscle on Thursday, hours before he was scheduled to start, and called up right-hander Don Heinkel to take his place against Houston. Power was the seventh Cardinals player to suffer a rib-cage injury in the last two seasons, the third this season and the second in five days. Relief pitcher Todd Worrell, who leads the team with six saves, was placed on the 15-day disabled list on Tuesday after injuring his rib-cage on his only pitch Saturday night.