Prater, a former five-star recruit out of Proviso West High School near his hometown of Chicago, Ill., said the decision was made so he could be "closer to my family." He said he addressed the issue with USC head coach Lane Kiffin on the phone last week and was given his release paperwork Monday.
"I just told him it was a decision that was best for me and my family. It had nothing to do with USC. I love the school," Prater said.
"It was hard. It wasn't easy."
Prater spent the holiday break with his family in Chicago, where he started to feel torn about playing so far away from his hometown.
"Over break a lot of things me and my family talked about and we thought it'd be a better decision to be closer to home."
While the 6-5, 215-pound "X" receiver wouldn't disclose the family matter, he said he got the support of USC athletic director Pat Haden before anyone else.
"I talk to Haden first on the phone, before I got to L.A. I talked to him before anyone else," Prater said. "He said he was going to support me wherever I go."
After letting the news settle with Kiffin for a week, his meeting with the head coach wasn't any easier.
"No coach wants to see their player leave. He told me that next year will be big year and what not," he said. "But he knows where I'm coming from. Only Kiffin knows what happened in that conversation."
Prater took a final lap around Heritage Hall Monday where he got emotional saying goodbye to the Trojan family.
"It was hard seeing all my teammates, seeing everybody in the administration today. It was hard," he said. "I love the school, I love the fans. I love the environment at USC."
Many questioned the touted recruit's lack of playing time. In the 10 games that list Prater's participation in 2011, he only caught one pass for six yards.
A penchant for injuries was thought to be the main reason for his lack of production. Prior to redshirting his freshman season, thumb and hamstring injuries set him back in spring 2010, followed by a foot injury in spring 2011. This past fall an ankle injury sidelined him for some of the Trojans' practices.
So what's in store for the player who was named the second-best receiver in the nation in the class of 2010?
In addition to a visit to USC, Prater took visits to Illinois and Notre Dame during his recruiting process. He said the Trojans' rival will not be on his future list but the Fighting Illini could very well be.
"I think my phone will go off tomorrow after the news today. I'm looking forward to it, I'm anxious though.
"At heart I'm going to always be a Trojan."