Pittsburgh’s highly touted Rule 5 acquisition, rookie outfielder Roberto Clemente, debuts his new uniform number, 21 (as reported by Pittsburgh Press beat writer Les Biederman). Originally number 13, he replaces the previous 21, outfielder Earl Smith, who was optioned to New Orleans of the Southern Association on May 3rd. Clemente is the 15th and final Pirate to wear number 21, which will be retired in 1973, following his fatal airplane crash on New Year’s Eve, 1972.

The second game of a Giants-Pirates doubleheader is called at the top of the 9th due to rain, 28 minutes short of the Sunday curfew, with the Giants leading, 5 – 3. If the rain had started before the end of the 8th, the game would have gone to the Pirates by a score of 3 – 2. The umpires almost rule it a suspended game rather than a called game, because they feel they have to wait at least half an hour before calling a game, which would set the time two minutes after the curfew. But a Giants vice president finds the rule that puts weather and similar conditions first when determining whether a game is called or suspended.

In Milwaukee, Cubs pitcher Warren Hacker loses his no-hitter when he gives up a one-out 9th-inning home run to George Crowe. Hacker holds on to win, 2 – 1.

After defending MVP Willie Mays opens the scoring with a 1st-inning single, his recent pupil, Pittsburgh’s rookie phenom Roberto Clemente, leads off the bottom of the frame by launching homer #3 off Sal Maglie, a rocket to left center that, according to Rud Rennie of the New York Times, touches down some unspecified distance beyond “the ivy-clad left-centerfield wall to the right of the 406-foot mark.” While the Giants untie the game with a two-run 4th, Maglie is busy shutting down the Bucs, allowing only two runners to reach second base until running out of gas in the 9th. He leaves the game with two on, two out and New York ahead, 3 – 2. Clemente then faces reliever Marv Grissom, who saves the win. Les Biederman of the Pittsburgh Press writes: “Clemente went after Grissom’s first pitch and lined it to Mays, who made the difficult catch seem easy and the fans who had congregated in the aisles left muttering and shaking their heads.”

At Fenway Park, the Cleveland Indians score 11 runs in the 5th inning to beat the Boston Red Sox, 19 – 0, and give Herb Score an easy win over Willard Nixon. The big blow in the inning is a grand slam by Vic Wertz. It is the worst shutout pasting ever by Boston and the most runs ever in a shutout for the Indians.

Chicago’s Dick Donovan tosses his third shutout of the season, beating the Senators, 3 – 0.

New York’s Irv Noren hits an inside-the-park grand slam in an 8 – 4 victory over the A’s. New York wins the nitecap to sweep the A’s. Mickey Mantle is 4 for 9 for the afternoon and is hitting .311.