"I hadn't heard anything about the school until they started recruiting me," he said after Wednesday's workout at the Staples Center.
Assistant coaches Harris Adler and Horace "Pappy" Owens first saw Peterson on the AAU circuit, and La Salle started recruiting him heavily.
Peterson won state titles in his junior and senior seasons at Hopkins High before he attended Lee Academy, a prep school in Maine.
Even as a high school senior, he didn't put up outlandish numbers, averaging 14 points, 6 rebounds, and 5 assists.
The number that stuck with the La Salle coaches was 61-2, the record of his high school team during his junior and senior seasons.
"He is just a winner," Owens said. "I would follow him around in the summer, and even those teams would win."
Entering Thursday, Peterson was averaging 4.0 points, 2.5 rebounds, and 1.5 assists. However, he has fit in well with La Salle as a strong defender.
"He does so much that doesn't show up in the box score," Owens said. "He is going to take the right shot, make free throws, box out, and make the right pass, and at 6-5 he can play multiple positions, including point guard."
Peterson, whose sister Kylie is a standout senior sprinter at the University of Minnesota, said he chose La Salle over Rhode Island and Fresno State.
"It felt like a family when I visited," he said. "Every guy on the team seemed to be a genuine guy and a person you could trust, and there are wonderful people on the coaching staff."
Peterson said he has been hearing from many people in Minnesota and is proud to be one of the few from his state to be competing in the Sweet 16. Marquette senior guard Trent Locket, also a graduate of Hopkins High, and Wichita State sophomore Jake White hail from the North Star State.
"In Minnesota, they love what La Salle is doing," Peterson said.
Peterson, like many of his teammates, was thrilled to be at the Staples Center, the home of Kobe Bryant and the Los Angeles Lakers.
"It is definitely cool playing in the same arena where Kobe, one of the best of all time, competes," Peterson said. "You can definitely feel him out there."
Peterson said he is not surprised by the Explorers' run. The Explorers went 21-13 last season, earning an NIT bid.
"Two years ago, people probably thought we wouldn't be in this position, but everybody in this room felt we could make a run," he said.