After Martin failed as both a first and third baseman, he was converted by the White Sox to a fine-fielding catcher. He particularly excelled at handling the floating knuckleballs of Hoyt Wilhelm. On September 10, 1967, he caught Joel Horlen’s no-hitter. That winter, the Mets acquired him to back up Jerry Grote.
Though a weak hitter, Martin is best remembered for two pinch-hitting appearances for New York. In the 1969 LCS opener, he delivered a key bases-loaded single. When he came off the bench in the bottom of the 10th in Game Four of the World Series, he triggered one of the most controversial plays in post-season history. He bunted to Baltimore pitcher Pete Richert, whose throw to first struck Martin on the wrist and ricocheted into short right, allowing pinch runner Rod Gaspar to score the winning run from second. Orioles manager Earl Weaver, who had been ejected earlier, saw the play and protested after the game that Martin had run illegally inside the foul line. Umpire Shag Crawford thought otherwise.