Gary Carter, the all-star catcher, makes about $1.8 million a year under his Montreal contract--and here's the Expos' chairman regretting that eight-year, $15 million signing before 1982 season.

Boss Charles Bronfman says, "We thought we couldn't win without him," but, "Two months before Carter signed, we were perfectly aware we were making a mistake. The next day and a month later we still knew we were wrong. I'll know it until my dying day. And I'm not just saying that because Carter had a bad year (this year)" . . .

After 21 years as Detroit Tigers' general manager, Jim Campbell is turning the post over to Bill Lajoie. An Orioles' bonus signee, Lajoie played 10 years in the minors, joined the Tigers as a scout in 1968, now moves up from v.p. in charge of their farm system. Campbell, in poor health recently, retains the title of chief executive . . . The general manager at AAA Portland, David Hersh, says he is hiring on as New York Yankees' director of player development--"a chance to be No. 3 man in one of baseball's champagne organizations . . . George Steinbrenner, Murray Cook (g.m.) and then myself."