Tom Seaver made his return debut with the New York Mets yesterday after a 5 1/2-year absence, and the 38-year-old right-hander dueled four-time Cy Young Award winner Steve Carlton, the 38-year-old left-hander, through six shutout innings before straining a muscle. Then Mike Howard's seventh-inning single off Carlton broke the tie and the Mets beat the Philadelphia Phillies, 2-0, for a major league record-tying ninth straight season-opening victory.

A crowd of 46,682, largest on opening day at Shea Stadium since 1968, turned out to watch.

"It's great to be back," Seaver said. "It was a great reception, and when something like that happens you don't want to go out and fall flat on your face."

Seaver, traded to Cincinnati in 1977 after 10 1/2 seasons as star of the Mets, was making his record-tying 14th opening-day start. He allowed only three singles before leaving the game with a strained left thigh, first hurt this spring.

Manager George Bamberger said he saw Seaver signal from the mound in the sixth that his leg was stiffening, "and he said when he came in after the inning that he might pull the muscle."

The Mets batted for Seaver in the bottom of the sixth, then rookie Doug Sisk allowed two hits and two walks and struck out three for his first major-league victory. He retired Mike Schmidt and Tony Perez for the last two outs with the tying runs on base.

Dave Kingman, after 12 Mets had been retired in a row, opened the home seventh with a single, the third hit off Carlton. George Foster singled and Hubie Brooks loaded the bases with a bunt single.

Howard, a surprise starter in right field, hit Carlton's next pitch between third and short, scoring Kingman and advancing Foster and Brooks. Brian Giles flied deep to right to score Foster.

The Mets tied the modern major-league record of season-opening victories set by the St. Louis Browns of the AL between 1937 and '45. The all-time mark of 10 was set by the NL's Boston franchise in 1887-96. Seaver tied the major-league mark set by Walter Johnson of the Washington Senators.