Number selection is never an easy process in Boston given the number of retired digits. But why did Johnson settle on No. 90?
“Every number, 1 to 34, is basically retired," said Johnson. "My first initial number, I picked No. 5, but I know there was going to kind of be some controversy with that because Kevin Garnett won a championship [wearing that number in Boston]. So I knew that was pretty much out the water.
"My [last] number  of course was retired [for Tommy Heinsohn]. I recently posted a picture on my social network, I don’t know if you guys checked it out, it was a team back in the '90s -- like ’97, ’96 -- that I played for. My first organized basketball team which was the Burbank [Calif.] Celtics. It was a Celtics team, so I just kind of put that together."
Then Johnson bottom-lined it: "The '90s were good. I was born in '87 but the '90s were good."
Johnson had hinted during his first chat with Boston reporters in Vegas earlier this month that he had been considering a jersey number in the 90s. It certainly worked well for Jae Crowder, who picked No. 99 after being acquired by Boston last season and signed a five-year, $35 million extension with the team on Monday.
According to the number register at Basketball Reference, Johnson stands to be only the second player in league history to wear No. 90. Drew Gooden has worn it with six teams during his 13-year NBA career.
Now well-versed in Boston's jersey numbers, Johnson said his next goal is to learn more about the city.
“I don’t know too much about the city, but I’ll definitely learn quickly. I get around," said Johnson. "I’m excited to see what kind of food places. I'm a big food person and heard about the clam chowder. I definitely know the fans will love me. I’m a team player, I’m a hustler. You guys know my game; I play hard every game. So I know the fans will definitely love me. I know they’re great fans. I know, back in the Detroit days, I’ve seen how rowdy they can get. So I know Boston loves their team for sure."
Despite being a native of Los Angeles and calling Las Vegas home in the offseason, Johnson said that, after playing for the Detroit Pistons and Toronto Raptors, he's accustomed to the wintry weather that awaits him in Boston.
“I turned into like an East Coast guy now," said Johnson. "I’ve been in so many winters, every kind of snow possible. When I first did it, I was definitely off of it. But you kind of get used to it now. So I guess I’m an East Coast guy now."
Celtics president of basketball operations Danny Ainge noted that he's watched Johnson grow up in the NBA and marveled that he's already a veteran of 10 seasons after being the NBA's last prep-to-pro player.
During Monday's introduction, Ainge again suggested that Johnson is a "winning player" capable of helping the Celtics build off last season's success.
"The score always seems to go in your favor when [Johnson is] on the court. He’s a guy that doesn’t necessarily fill up a stat sheet like a lot of players, but he is a winning player," said Ainge. "He’s a guy that his teammates love playing with. He plays great defense, he rebounds, defends multiple positions and brings a lot of versatility."
Asked about his impressions of Boston's team while playing for Atlantic Division rival Toronto in recent seasons, Johnson saw similarities to the Raptors.
"Energy. I felt like the Celtics this year were kind of like [the Raptors] when we first made the playoffs back a couple years ago," said Johnson. "They’re on the rise to be better. I kind of got that impression of [Boston] last year... I feel like we can take it to another level. So that’s the impression I got. Young team, hungry team, and I’m happy to be a part of it."