The Red Sox did not say who will replace Rodriguez (1-3, 8.59 ERA) in the rotation. They recalled right-handed reliever Pat Light from Triple-A Pawtucket on Tuesday. Light, 25, made his Major League debut on April 26 against Atlanta, allowing two runs on two hits in one inning. He went 5-for-5 in save opportunities while posting a 2.05 ERA in 20 outings.
Pawtucket lefties Henry Owens and Roenis Elias would seem to be the top internal starting candidates, though neither made much of an impression in previous stints with the Red Sox this season.
President of baseball operations Dave Dombrowski will continue to work the phones, but he said Sunday there isn't much movement on the trade market at this point.
"I have to remain focused on the guys internally here," said Red Sox manager John Farrell. "Whether there's an option that is an upgrade internally, that's one thing. But to say that someone else is going to walk through that door from another organization, I'm not banking on that."
After a strong rookie season by Rodriguez, his sophomore campaign got off to an ominous start when he suffered a right knee subluxation on Feb. 27.
Rodriguez favored the knee during various portions of his Minor League rehab assignment, and he then developed some delivery flaws.
Rodriguez provided some hope by faring better in the start that preceded Monday's, giving up three earned runs over six innings last week against the White Sox. But this start was a significant step back.
"Just missed spots and didn't throw the pitch like I have to throw in that count," said Rodriguez, who spoke to reporters before the roster move was made. "So that's what happened. It felt like I don't find the spot good with the pitches that I wanted and the count I wanted. That's all."
Red Sox second baseman Dustin Pedroia became visibly frustrated with Rodriguez during the game, appearing to tell him in a mound visit to stop worrying about previous mistakes and to focus on the next pitch.
"What did I say to Eddie? Do you honestly think I'm going to tell you that? I was talking to him about baseball," Pedroia said. "I talk to all my teammates, every day. That's about it."