When Left-hander Jim Kaat of the Twins held the White Sox to just three singles and beat them 1-0 last week, he became the first 20-game winner in the American League this season. Until then, few people had paid much attention to Kaat. Nobody has ever paid much attention to him, something that was evident after the second game of last year's World Series when most of the talk centered around losing Pitcher Sandy Koufax rather than around winning Pitcher Kaat, who had given only seven singles in a 5-1 victory. In fact, in the fifth inning of Kaat's 20th win, Owner Calvin Griffith of the Twins left to catch a plane. Anonymity comes easily to Kaat. Hardly anyone recalls that he won 18 games in 1962, 17 in 1964 and 18 again last season. Or that now, at the age of 27, he has amassed 93 big league wins. One of the few times anyone has noticed Kaat's pitching was years ago when his father caught him ducking out on lawn-mowing chores to play ball. "You can't make a living playing ball," said the elder Kaat. "You have to learn to work." Jim played ball, but he compromised by becoming a hard-working ballplayer. He worked to overcome a bad habit he had of pitching across his body; he worked hard on his control; he worked to develop a pitch he calls his "slurve," which is part slider, part curve. Now, with a 20-victory season, 24? consecutive scoreless innings and a 2.78 ERA, maybe people will finally begin to notice Jim Kaat.