Johnson has been scratched from his scheduled start for Triple-A Pawtucket on Friday, Alex Speier of The Boston Globe reports.
With David Price headed to the disabled list with elbow soreness, Johnson will presumably be Price's replacement for the Red Sox on Friday, although that hasn't been officially confirmed. The 26-year-old has a 4.33 ERA and 1.48 WHIP over 27 innings during four stints with Boston this season.