Collison will undergo surgery on both shoulders. The left one was dislocated in a practice session last week. An MRI revealed a similar injury to the right one.
"It was an awkward movement, and I felt the shoulder basically pop out for a second and pop back in," Collison told the Seattle Times about injuring the left shoulder. "Tuesday morning, I reached for a ball again and it slipped out again. Then we decided to get the MRI done. I tried to find someone who would say that I could play, but I couldn't find one."
It is anticipated that Collison, the team's 12th pick out of Kansas in this June's draft, will need six months recovery time, and a full recovery is expected.
He was the lone collegian to play this summer for Team USA in the Olympic qualifying tournament at San Juan, Puerto, Rico.
Notable deaths of 2014 [PHOTOS]
UPI Sports Results for September 19, 2014