BASEBALL COMMISSIONER Peter Ueberroth made another pitch for drug testing of major-league players this week. The leadership of the players' union, acting the same way it did when Mr. Ueberroth raised the issue last spring, ducked and shouted beanball while the pitch broke over the outside corner for a strike. Mr. Ueberroth has seized the moral high ground in baseball, even if that's only about the height of a pitcher's mound these days, and he is making good use of it while he can.

Publicity from two drugs-in-baseball trials in Pittsburgh provided a perfect backdrop for his latest action. He sent every player in the major leagues a plea to submit to testing for possible drug use in the 1986 season, and asked for an answer by the end of the week. "Baseball is in trouble," the letter said. "The shadow that drugs have cast is growing larger and darker by the day. It threatens you, your families and all of us who make our living from and take pride in the game."

Don Fehr, acting executive director of the players' union, denounced the letter as an attempt by the commissioner to go around the union and negotiate directly with the players. If it was, it didn't work. The players have made it clear they're sticking with the union. But many of them have also showed considerable interest in some sort of testing arrangement -- just so long as the union has a large role in it. Perhaps they can lead their union leadership toward a reasonable accommodation.

Mr. Ueberroth may exaggerate the length of the shadow over baseball. In fact, the drug trials in Pittsburgh have evoked remarkably little indignation from fans, who are breaking all attendance records. Most people just don't want to worry about that sort of thing.

But Mr. Ueberroth is paid to worry about it, and has reason to do so. The use of illegal drugs, especially very expensive illegal drugs, opens the door to corruption of the game in many ways. More important, it confuses the children, who have an inordinate amount of faith in their heroes.

The civil liberties issue is raised by opponents of mandatory testing. But this sort of testing is a well- established tradition in many other sports, both amateur and professional, and doesn't appear to have caused any great distress for the athletes. Given the dangers of competing under the influence of drugs, it might even have saved some lives.