After playing at St. Catherine's High School in Racine and blocking a school-record 399 shots at Marquette University, McIlvaine was named NABC Defensive Player of the Year and was drafted with the fifth pick in the second round of the 1994 draft by the Washington Bullets. He spent two years with the team, primarily in a backup role to Gheorghe Mureșan. In limited playing time, McIlvaine averaged fewer than 15 minutesa game during his second year. In 1996, McIlvaine entered free agency.
Seattle SuperSonics signing
In 1996, the Sonics offered a seven-year, $33.6 million free-agent contract to McIlvaine. Seattle fans were upset, and so was superstar forward Kemp, who had been asking for a contract increase after leading the team to a franchise-record 64 wins and its best postseason performance in 17 years, including the third Finals appearance in franchise history. But because Kemp signed a contract extension in 1994, the NBA's collective bargaining agreement forbid any changes to that contract until October 1997. Despite fan derision, McIlvaine helped the Sonics win its division in each of his two years with the Sonics. Following the 1997 season, Seattle was involved in a three-team trade that sent Kemp to the Cleveland Cavaliers in exchange for the Milwaukee Bucks' Vin Baker, with the Cavaliers' Terrell Brandon and Tyrone Hill going to Milwaukee.
Final years
In his first season in Seattle, McIlvaine registered career highs in games, minutes, points per game, rebounds per game, and steals, while also averaging two blocks per game. His second season in Seattle saw him decline in every major statistical category, although he still posted numbers close to his career bests in most areas. Eventually, McIlvaine was dealt to New Jersey in 1998 for Don MacLean and Michael Cage, primarily to open up salary cap room. McIlvaine rounded out his career with the Nets, playing three injury-riddled seasons with the team. In 1999–2000, McIlvaine played 66 games in his best season since leaving Seattle, but injury problems and declining numbers continued to hamper him until his contract was bought out by the Nets after the 2000–01 NBA season. McIlvaine retired with an average of 2.7 points, 3.1 rebounds, and 1.71 blocks in 401 career games.
