On July 14, 1961 Roberto Clemente erases a 4 – 1 deficit with his two-out, 8th-inning, game-winning grand slam, hit “high and far into the black night, over the 410-foot sign in center-field,” according to Bob Stevens of the San Francisco Chronicle. UPI’s Scott Baillie elaborates, describing “a ball that took off low and gathered altitude like a jet as Willie Mays vainly scaled the left center field fence.” The Bucs tack on one more to beat the Giants by a final score of 6 – 4. The Chronicle’s Phil Berman collars Clemente for some post-game comments: “‘I was looking for an inside pitch,’ said Clemente. ‘I don’t know whether it was a fastball or not, but it came in a little inside and I was ready for it. I know it went out of here fast,’ he grinned. Although Clemente’s drive clears the centerfield fence like a shot, the Pirate outfielder recalls it is not the hardest ball he has hit here. ‘Last year I hit one harder to the left field bleachers (May 6, 1960). That was a high fly ball. But this was a line drive. And I liked this hit better because it won the game.'”
Source
Baseball Reference July 14