Costner graduated from Overbrook High School, in Philadelphia, in 1980. In 2012, Costner was recognized by the Philadelphia Daily News, as a Third-Team All City member, on its list of the "Best high school hoops players of the past 35 years".[4]
College career
Costner decided to stay in Philadelphia for his collegiate career. He played at the center position for the Saint Joseph Hawks, from 1980 to 1984. He averaged 14.4 points, 7.9 rebounds and 1.1 assists per game in his college career. As a Senior, Costner averaged 18.6 points, 8.3 rebounds and 1.2 assists per game, as Saint Joseph's finished the season with a 20–9 record, under head coach Jim Boyle.[5]
On December 30, 1983, Costner scored 47 points in a game versus Alaska-Anchorage, which still stands as the Saint Joseph's single-game scoring record.[6] During his college career, Costner was an Atlantic 10 All-Conference selection in his junior and senior seasons, a three-time All-Big 5 selection, and an Associated Press Honorable Mention All-America selection in 1983. In his college career, Costner scored a total of 1,730 career points, to go along with a total of 951 career rebounds.
Professional career
On June 19, 1984, the NBA's Washington Bullets, selected Costner in the second round, with the 34th overall pick of the 1984 NBA draft. Costner went on to play pro club basketball in Europe, starting his career with Basket Napoli. With Las Palmas, Costner averaged 20.4 points, 10.1 rebounds, and 0.9 assists per game, in 21 regular season games played, during the 1985–86 season. He spent the 1987–88 season with A.P.U. Udine.