Hainje joined the Butler Bulldogs beginning the 1998–99 season after graduating from and playing basketball and football at Cathedral High School in Indianapolis.
In his final season with Cathedral, Hainje averaged 16.8 points and 9.0 rebounds, 2.5 assists, and 1.9 steals per game and was named Indianapolis "City Player of the Year".
[1] In his junior season, Hainje started all 32 games, was named to the MCC All-Defensive Team, earned a spot on the MCC All-Tournament team, became the first player since 1997–98 to lead Butler in scoring in three consecutive games (Evansville, Indiana State and UNC-Wilmington), the first Butler player since '97–98 to post back-to-back 20-point performances (Evansville and Indiana State), led the Bulldogs with five 20-point efforts, finished second on the team in rebounding and field goal shooting, and ranked fifth in the conference in field goal shooting.
Notably, Hainje had team-highs of 18 points and six rebounds against Arizona in the Fiesta Bowl Classic, less than four hours after being treated at a hospital for flu-like symptoms.
After graduating from Butler, Hainje considered a return to football as an NFL tight end, and the Indianapolis Colts sent him through a private workout.