The 26-year-old forward was dropped from a game in
mid-May after missing a team meeting. That followed post-game comments he made demanding more of the ball from his teammates.
Without Johnson, RSL recorded its biggest win of the season on Saturday, a 4-0 victory over Eastern Conference leader Philadelphia.
Johnson moved from his native Liberia to Sweden when he was 18 and played at clubs in Sweden, China and Norway before joining RSL.