Keith Hernandez drove in three runs and Wally Backman had three hits and three runs scored as the Mets beat the Philadelphia Phillies, 4-3, last night in New York for their eighth straight victory.

The Mets maintained a one-game lead in the National League East over St. Louis, which beat Pittsburgh, 8-1.

Winner Sid Fernandez (4-6) struck out 13 and took a one-hitter into the ninth inning. In the ninth, Rick Schu doubled and Mike Schmidt got a bunt single, and Roger McDowell relieved Fernandez. McDowell gave up a three-run homer to Glenn Wilson and was replaced with one out and one on by Jesse Orosco, who earned his 12th save.

Philadelphia's only hit before the ninth was Garry Maddox's bloop single with two out in the second.

"I no longer have any self-doubt," said Fernandez, a 22-year-old left-hander. "Now, I believe in myself. No question, I was disappointed in not finishing, but I respect the manager's (Davey Johnson's) judgment. I understood that he was trying to help me get the win, and thinking about it now, he definitely made the right decision."

Johnson, booed loudly as he returned to the dugout after bringing in McDowell, said, "Sid had thrown 133 pitches. I figured a fresh McDowell would help him get the victory. This is the third time that Roger has given up the (home run) in relieving Sid, and I'll remember that for the future. I wanted badly for Fernandez to win, but by the same token, I didn't want to push him too far."

The Mets, who have won 29 of their last 36 games, took a 1-0 lead in the first off loser John Denny (7-9). Len Dykstra walked, Backman reached on a force play and scored on Hernandez's double. It was Hernandez's league-leading 19th game-winning RBI.

The Mets scored twice in the third with two out. Dykstra singled and scored on a double by Backman, who extended his hitting streak to 11 games. Hernandez drove in Backman with a single.