Originally signed by the Phillies, Martinez fashioned a seventeen-season career on defensive talents. Although a .283 hitter in five minor league campaigns, he hit over .250 only twice in the majors. He was slow afoot and hit with power infrequently. He was, however, excellent at blocking home plate, had an accurate arm, and handled pitchers well. Martinez was most productive in platoon situations, first with Bob Stinson at Kansas City, then with Charlie Moore in Milwaukee, and finally paired with Ernie Whitt for Toronto. In 1976 he tied Jim Sundberg for best fielding average (.991) among AL receivers.
Martinez never fully recovered from a fractured leg and dislocated ankle sustained while blocking home plate in July 1985. After tagging out the lead runner and suffering the broken leg, he threw to third from the ground. It was a bad throw, and that runner came home too; Martinez managed to take the throw and tag him out as well.
Martinez worked as a broadcaster for the Blue Jays and ESPN until November 2000, when he was hired to replace Jim Fregosi as the club’s manager.