Drew Williams, a senior at Lane Tech High School, collapsed on the sidelines after taking a hit during a game Friday, WBBM-AM, Chicago, reported.
The student, who played running back and cornerback, was in intensive care after undergoing surgery to relieve pressure from swelling on his brain, Williams' coach said.
"I know he's going to get through this," teammate, Richie Costas, a junior, said as he came to class Wednesday. "It's scary. We were right there."
Counselors have been made available to students experiencing difficulty dealing with Williams' injury.