Johnson has rejoined the rotation at Triple-A Pawtucket after being shut down with shoulder fatigue.
Johnson has allowed two runs over two starts (nine innings) since returning from the shoulder issue that cost him one turn in the rotation. With David Price (elbow) sidelined, the left-handed Johnson is an option as a fifth starter if the Red Sox feel Doug Fister, who was hit hard in Monday's loss to Cleveland, isn't working out.