Up against the host school at the prestigious event, Johnson went 11-for-11 from the field on his way to 23 points and 10 rebounds.
"I just tried to get my game started early," Johnson said of his performance. "Just play hard and get my team into it, that's what I tried to do."
Johnson, a 6-foot-10, 235-pound center, has transformed his body over the past year. He's in great shape and he credits extra work with his personal trainer.
"The past couple of months, I've been doing some extra work with my trainer," the five-star recruit said. "Just weight lifting, the treadmill and the incline, we've been going hard on that."
"I think I've gotten in much better shape and I run up and down the court much better," he said about his improvement. "[I'm] just working on my skills now offensively and keeping on pushing it and getting better athletically."
While talking to a group of reporters after his impressive outing, Johnson shared some news.
Johnson broke down each of his three finalists:
Kentucky: "Kentucky is a very good school. I like John Calipari. Not just because of all the one and dones, but how he develops his players. If you go there, you really have to work hard."
Syracuse: With Syracuse I have a really good relationship with Adrian Autry and coach Boeheim. They are real good."
Georgetown: "Then Georgetown is a big man dominant school and a lot of good big men have come out of there."
Johnson, Scout.com's No. 15 prospect in the 2013 class, didn't claim a favorite. He did, however, spend a considerable amount of time in Lexington, Ky., as he went to middle school at Lexington (Ky.) Sayre.
"It's pretty big," he responded when asked about the significance of his time there. "I have a lot of good friends there and a lot of extended family, so it's a big deal."
Johnson didn't mention a timetable for making his college choice.