Outfielder Greg Harts spent six seasons in the Mets organization but appeared in just three games at the big league level. He made his Major League debut as a pinch hitter for pitcher Buzz Capra on September 15, 1973; he singled to centerfield. Harts made two more appearances for the Mets one as a pinch runner on September 17 and another as pinch hitter on September 20.
Following the 1973 season Harts returned to the minors. In 1975, he tried to convert to a pitcher but ended the experiment after posting an 0-2 record with a 5.90 ERA in 19 appearances, though he did manage to save four games
Harts retired from playing following the 1975 season.
While with the Mets Harts wore number 6.