Raised in Belmont, Massachusetts, Wood played several sports in high school and was signed by his hometown Boston Red Sox in 1960. He pitched sparingly for them over parts of four seasons before being traded to the Pittsburgh Pirates in 1964. Seldom-used by the team in 1965, he spent all of 1966 in the minor leagues before being traded to the White Sox. Wood, who had previously relied on a fastball and curveball, refined the knuckleball with the help of veteran knuckleball specialist Hoyt Wilhelm. He spent the next four seasons as a relief pitcher for Chicago. In 1968, he set a record (broken the next year) with 88 games pitched, getting named the "Sporting News" American League (AL) Fireman of the Year.