"The most frustrating thing was just having to watch the team play and not being a part of it," Johnson said.
Instead of working on his skills during practices and games, Johnson was forced to develop his game with individual workouts.
"I'd just go to the gym by myself," he said.
Johnson played with Cal Team Select last summer, but he hasn't decided where he'll play this year. It could be with Pump ‘N Run or a new team run by former USC assistant coach Dave Miller.
"I don't really have any idea right now," Johnson said. "I just know that I need to make up for lost time."
Johnson, ranked the No. 6 junior in the nation by TheInsidersHoops.com's Dave Telep, will do his best to show college coaches that he's one of the elite frontcourt players in the country.
For now, his favorite school is North Carolina.
"I know that a lot of good players came out of there," Johnson said. "It's a great school and they've sent tons of guys to the NBA."
Maryland, Louisville, Kentucky, Georgia Tech and Syracuse were also mentioned while Johnson has, in the past, also prominently spoken about Arizona and Florida State.
"It changes every week with him," said his father, Anthony Johnson. "He really doesn't know."