Mack was the 11th player selected in the 1st round of the major league draft in 1984. Following college, he played on the U.S. Olympic baseball team which won a silver medal in the 1984 Olympic Games in Los Angeles. Subsequently, he played nine professional major league seasons. His career statistics include a .299 lifetime batting average, 80 home runs, and 398 RBIs in 923 games. Mack started his career with the San Diego Padres. In 1990, he was selected in the rule 5 draft by the Minnesota Twins where he starred from 1990-1994. Notably, he was a key component of the Twins' 1991 World Series championship team. In 1992 Mack had his best year, hitting .315 (fifth in the American League), scoring 101 runs (seventh in the AL), stealing 26 bases, driving in 75 runs, and hitting 16 home runs.
On March 6, 2006, having been informed of the condition of former teammate Kirby Puckett, who had gone blind a few years before and suffered a massive stroke the previous day, Mack flew to Arizona to be with him along with a number of other current and former Twins; Puckett died later that day.
His brother is former major league outfielder Quinn Mack.