Martinez, 39, is in his 16th season (or 17th, if you include the 2012 season he missed due to injury). He came up with the Cleveland Indians as a catcher, spent parts of 8 seasons with them, and was traded to the Boston Red Sox during the 2009 season. After 2010, he joined the Detroit Tigers as a free agent, and has been with them since.
Martinez was primarily a DH once he went to Detroit, but regardless of his position, he was, for most of his career, a quality hitter. A switch-hitter, he put up a career .295/.359/.455 slash line, with a career 32.2 bWAR, though he has struggled the past several years.
Martinez isn’t a Hall of Famer, but he was a really good player who had a really good career. Best of luck to him in his post-playing days.