Hayden was called up from the minor leagues in the middle of the 1958 campaign, and pitched in three games for Cincinnati. He was effective in his first two outings, hurling a total of 2+1⁄3 scoreless innings on June 26 and June 30 against the San Francisco Giants and Milwaukee Braves, respectively.[3] But in his third appearance, against the Philadelphia Phillies on July 6, he gave up four hits, a walk and two earned runs in only one inning pitched.[3] The next day, he was returned to the minor leagues when Cincinnati called up outfielder Danny Morejón.[4] Hayden did not return to the major leagues. He played for the minor league Havana Sugar Kings and Nashville Vols during the 1958 season, his last in professional baseball.[2]
During his baseball career, Hayden pitched in a total of 165 minor league games, compiling a win–loss record of 53–46.[2] While sometimes referred to as "Lefty", a common nickname for left-handed pitchers, Hayden was primarily called "Gene".[5] In 1960, he was hired as a police officer in Rio Vista;[6] he was still with the department in 1969 as a sergeant.[7] As of November 1992, Hayden was working at a substance abuse treatment center in Herald, California, and noted that he was a recovering alcoholic and had spent 1980 homeless in Los Angeles.[8] Hayden died in Lodi, California, at age 68 in 2003.