BALTIMORE -- Christopher Johnson, who had been classified as the likely candidate to fill in for Eduardo Rodriguez in the Red Sox rotation, is now iffy after tweaking his right hamstring in a start for Triple-A Pawtucket on Saturday night.
The left-hander, who pitched a shutout on May 27 at Fenway Park, fell down after his hamstring locked up on him while making a pitch in the second inning at Durham. Johnson exited the game at that point, and received treatment from the Pawtucket training staff on Sunday.
"He's improved throughout the day," said Red Sox manager John Farrell after a 7-3 win over the Orioles. "Over the coming days we're hopeful we can get him back on the mound and get a bullpen. Until that time, we just know that he's improving."
The Red Sox had been looking to insert Johnson into their rotation either Friday or Saturday at Fenway Park against the Tigers.
"He's in the mix, there [hasn't] been a final determination yet," said Farrell.
The 26-year-old Johnson has made two spot starts for the Red Sox this season, going 2-0 with a 2.57 ERA.
If Johnson can get healthy in the next few days, his stint in the rotation could be at least a little more extended depending on how quickly Rodriguez recovers from a right knee subluxation that led to him going on the disabled list on Friday.
The candidates after Johnson are Henry Owens, Kyle Kendrick and Hector Velazquez.