Mays hit 52 home runs in 1965, joining Ruth, Jimmie Foxx, Ralph Kiner, and Mantle as the only players at the time to hit at least 50 in a season more than once. On May 4, 1966, Mays surpassed the National League home run record of 511, held by former Giants outfielder and manager Mel Ott.
Even as he approached the age of 40, Mays was still capable of playing an excellent game, but he had changed.
“Willie, as he grew older, became more introverted and suspicious, more cautious, more sensitive and, for many reasons, more full of worries,” Leonard Koppett wrote in “A Thinking Man's Guide to Baseball” (1967). “Life became more complicated for him, both personally and professionally, and he suffered a number of setbacks.” Koppett wrote that after marrying and adopting a child, Mays “went through a painful divorce.”
On May 11, 1972, with the Giants' attendance declining, longtime team owner Horace Stoneham sent Mays to the Mets in exchange for a minor league pitcher, Charlie Williams, to provide him with long-term financial security.
Mays was in the next-to-last year of a two-year contract that would have paid him $165,000 per season (about $1.25 million today). When the deal was struck, Mets president John Payson, who was a shareholder in the New York Giants and a fan of Mays, guaranteed him an annual payment of $50,000 for 10 years in addition to his baseball salary. He was to be a goodwill ambassador and part-time trainer after his playing days were over.
Mays had a .167 average when he joined the Mets, but on May 14, in his first game with them, a Sunday before a crowd of nearly 35,000 at Shea Stadium, he beat the Giants with a home run. Yet he was 41, and his skills had diminished. The following year he struggled with sore knees, a swollen shoulder, and bruised ribs, and on September 20, 1973, he announced his retirement.