The 30-year-old suffered a heart attack during a fixture against Kelantan at the Sultan Mohd IV Stadium in Kota Baru.
Just three minutes into the match Oniya fell to the ground and was taken to hospital via ambulance where he was pronounced dead 30 minutes later.
T-Team chief executive officer Syahrizan Mohd Zain expressed his shock at Oniya's death.
“There was no hard running and it was a slow tempo match. It’s only a friendly game. The match was called off in the 60th minute when we received a call from the hospital that Oniya had died,” Syahrizan told The Star.
Syahrizan has hit out at the level of medical attention that Oniya was provided at the stadium.
“He suffered a heart attack but it could have been a different story had the ambulance driver was alert," he told the New Straits Times.
"The driver was at the stands watching the game when Oniya suddenly collapsed and our defender was deprived of oxygen for several minutes."
Oniya was in his first season with the Malaysian club, having previously played in Uzbekistan and Azerbaijan.