Johnson was optioned to Triple-A Sacramento on Monday, Henry Schulman of the San Francisco Chronicle reports.
Johnson spent almost the entire 2017 season with the Cubs organization at Triple-A Iowa. He pitched 54.1 innings across 44 games, posting a 4.31 ERA and 1.46 WHIP in the process. While his control was underwhelming (27 walks), he was able to consistently log strikeouts, as he fanned 74 batters in that time.