A strong right-handed pitcher, Runzi played in the farm system of the California Angels in 1993. He helped the Boise Hawks win the Northwest League championship. He also played for the Cedar Rapids Kernels in Cedar Rapids, Iowa. Runzi pitched for the University of Missouri at St. Louis from 1990 to 1993, helping his team advance to the College World Series in 1993. The UMSL Rivermen won the MIAA tournament in 1993 and Runzi was named MIAA Pitcher of the Year. His team won the Central Region Championship in 1993 and finished second in 1992. Runzi was named Central Region Pitcher of the Year in 1993. He was an All-American in 1992 and 1993, and he was also named to the All-Conference and All-Region teams. He holds the UMSL records for career wins, total innings pitched, and career shutouts. Twice, he struck out 11 batters in a game, and ranks fourth in career strikeouts at UMSL. Inducted in 2001, Runzi is one of the twelve original members of the UMSL Sports Hall of Fame. He played for Herculaneum High School and later became the head baseball coach at that school. He was a pitcher, infielder, and outfielder for Herculaneum High from 1986 to 1989. His team won the Class 3 Missouri State Championship in 1986. He played on two conference championship teams and two district championship teams. He was named All-Conference three times and All-District three times. He was chosen for two All-Metro teams, and two J98 Dream Teams. He was named All-State in 1989. That same year, he played in the East-West All-Star Game. Runzi was the head baseball coach at Herculaneum High School from 1996 to 2006. In 1999, his team won the Class 3 Missouri State tournament and he was named Coach of the Year. As head baseball coach, he won eight conference championships, five district championships, and two sectional championships. The Jefferson County Athletics Association named him Coach of the Year seven times. Twice, he was chosen as the J98 Dream Coach of the Year. In 1998 and 1999, he was selected as a coach for the East-West All-Star game. In 1995, Runzi was the assistant baseball coach at Herculaneum High School. His team finished second at the Class 3 Missouri State Tournament Runzi is a past vice president of the Missouri State High School Baseball Coaches Association. He pitched for Mineral Area Junior College from 1989 to 1990. From 1987 to 1989, he played for Festus American Legion Post 253, helping his team win the district championship all three years. In 1987, Festus won the Zone Championship and finished fourth at the Missouri State American Legion tournament. From 1994 to 1996, he was the assistant baseball coach of the Festus American Legion team. Runzi played in the CYC League for the Condair Royals in 1989, and the St. Louis Indians in 1990 and 1991. He was selected to the CYC all-star team as an outfielder in 1991. In 1992, he pitched for the Fairview Heights Mets in the Central Illinois Collegiate League. In 1994 and 1995, Runzi was a pitcher for the St. Louis Union Printers. In 1994, he received the “Grit Award” for being one of the top pitchers at the Printers national tournament.