Ilijevski, 58, complained of pain and dizziness after making a save in Saturday's game and was diagnosed with having a rupture in the wall of his aorta.
He underwent surgery and was then placed on life support. He died on Monday after a decision was made to remove the life support.
The Macedonian-born Ilijevski was one of the best goalies during the heyday of the MISL. He held the league all-time record for games played by a goalie (391).
"Slobo and I came up at the same time. He was very fit for his age, his work ethic was second to none," Tony Glavin, former teammate and later coach with the St. Louis Steamers, told the St. Louis Post-Dispatch. "Even though he was 10 years my senior, he certainly didn't use it in a negative way when I became coach. He was nothing but great to work with. When the team was having financial difficulties, Slobo stayed and accepted less money; he was just that kind of person. The man played through his 40s in professional soccer, which is phenomenal."
Ilijevski owned apartment buildings in the St. Louis area and ran soccer camps. In recent years, he lived in San Diego.