LeBron James has been working out with teammates in pickup games at the team's El Segundo practice facility.
Johnson said he can see how James is making the Lakers' young core better simply by facing him again and again in the games.
"When you play against him every single day, you get better," Johnson said.
James himself hasn't spoken to the Los Angeles media since his blockbuster free-agent signing this summer. He's expected to speak for the first time in a press conference on Monday.
The Lakers season opens Oct. 18 at Portland and the first home game is Oct. 20 vs. the Houston Rockets.