Roy Sievers . . . Jim Lemon . . . Cookie Lavagetto . . . Harmon Killebrew . . . Bob Allison . . . Camilo Pascual . . . Mickey Vernon . . . They're all due in town, those grand old Washington Senators, for the Alexandria Grandstand Managers' 25th anniversary party May 28.

But they'll probably call for a moment of silence on that occasion at Belle Haven Country Club: Cap Peterson died over the weekend.

He was Charles Andrew Peterson (C.A.P., hence, "Cap"), outfielder on the 1967 and '68 Nats. Long plagued by kidney problems, he died in Tacoma, Wash., on the weekend, at age 37.

Peterson was a .230 hitter for a 536-game major league career. He broke in with the Giants, and it was the Senators' luck to give up left-handed pitcher Mike McCormick for him (and pitcher Bob Priddy) -- after which McCormick promptly won 22 games and a Cy Young Award. Then, shortly before Washington consummated his 1969 trade to Cleveland, Cap smacked three home runs for the Nats in an exhibition game. Back in Tacoma, he headed Peterson Building Co., founded by his father, who used to pitch to the boy Cap with their Labrador retriever shagging the ball . . .

Before baseball 1980 prematurely fades into nostalgia, too, if the strike is to be, a full ration of diamond controversy:

For instance, Billy Martin, already cocky enough that he is expressing impatience with owner Charlie Finley: "He's waiting around to see how we do, and if we do well, he's going to take all the bows. I'll tell you something, I've dealt with owners like that before, and I didn't take then and I'm not going to take it now."

Martin's wrath was piqued by a dearth of right-handed hitting -- "There's no way we're going to beat a team like Chicago which has five lefthanded starters" -- and Finley's failure to provide any . . .

For instance, Jimmy Piersall in a hassle over his criticism of some of the Chicago White Sox' play from his perch in the broadcasting booth with Harry Caray. The former flamboyant outfielder has verbally dueled with boss Bill Veeck and Veeck's wife, Mary Frances, who joins her husband in conducting a Sunday morning radio call-in show. "She knows nothing about baseball, has no idea of what's going on and she should be in the kitchen," Piersall said after "she said in her show that I'm picking on certain players . . . All I do is report what I see."

So the Chicago Sun-Times in its Sunday edition printed a ballot asking the fans to vote: "Should Jimmy Piersall be fired?" Piersall: "I'm talking to my lawyers about that."

For instance, Bob Horner filing yet another grievance against the Atlanta Braves. Horner and teammates Gary Matthews, Jerry Royster and Preston Hanna, that is, via the Major League Players Association, charging the club took improper disciplinary action in fining each of them $500 for missing an April booster-club lunch. Manager Bobby Cox originally fined them $50, reportedly; owner Ted Turner, a few days later boosted the amount ten-fold.

P.S. In case you missed it, Horner is hors de combat again, citing a sprained back -- hurt, he said, lifting logs at home . . .

Last night's honor by the Boys' Club of Greater Washington wasn't the last for Georgetown Coach John Thomspon. Wednesday night, the Pigskin Club of Washington will observe basketball night at its meeting at Howard U.'s Dumbarton Campus and salute Thompson and fellow coaches Lefty Driesell, Maryland; A. B. Williamson, Spingarn, plus Wood's star athlete, Earl Jones. That's Jones as in Bob Cousy Trophy winner as top high school player in America -- to be presented Friday in New York before the 6-11 former West Virginian plays in the Kutsher's Classic in Monticello, N.Y. Or as in Jones the Olympic trials invitee -- he flew off to Kentucky for those yesterday.

Another pro athlete admitting to, and going about conquering, alcoholism: Dennis Lick, Chicago Bear offensive tackle. The curse plagued him from the time he was 16 through his all-American days at Wisconsin, he says, now that he has completed a three-week treatment program and is saying, "Right now, I'm living 24 hours at a time" . . . Another of the Philadelphia Eagles caught in a drug bust last year gaining a new lease: fullback James Betterson. A Camden, N.J., judge placed him on 13 months probation yesterday as a possible prelude to dismissing two charges of possessing cocaine. The judge noted that the evidence was not overwhelming, Betterson has maintained innocence, and Eagle management calls the erstwhile Tar Heel "an outstanding young man, good citizen, good example for the young people."