The injury, similar to the one he suffered while with the Tampa Bay Rays last season, will be evaluated by Dr. Scott Ahmad in New York. From there, a decision will be made whether Eovaldi needs to undergo surgery that would keep him out for nearly two months.
However, both Red Sox president Dave Dombrowski and manager Alex Cora expressed they were not overly concerned that Eovaldi, who has had two Tommy John operations, would miss that much time.
Eovaldi said he didn't experience any symptoms after his start against the New York Yankees on Wednesday, when he tossed six innings while allowing one unearned run, walking one and striking out six. The 29-year-old knew something was wrong when he could not straighten out his arm during the team's off day in Tampa Bay.
It's just frustrating when you're coming off a good outing and you're taking the right steps forward, and you have to have this and you just can't throw," Eovaldi said. "For me to not be able to get full extension, I can't throw like that."
Dombrowski said there was a chance the loose body, described as cartilage, was there when Eovaldi underwent surgery in March 2018.
"We did an MRI when we signed him and we didn't see it," Dombrowski said. "It's so small that sometimes MRIs don't pick these things up. And sometimes, if you went in there for surgery, it could've been in a place where you couldn't see it. You're talking such a small piece, but it's just in the wrong place at this time."
Eovaldi's move to the injured list is retroactive to Thursday. Cora said the team will fill the gap in the rotation internally.
"We'll see how it goes the next few days," Cora said. "We've got Rick [Porcello] today, David [Price] and [Chris Sale] on Monday. We've got [Marcus Walden] and Hector [Velazquez] has thrown the ball well. He struggled with command in the last one, but the way he threw in Arizona, the stuff is a lot better. We'll see how he goes today and tomorrow and then we'll make a decision."
Eovaldi signed a four-year, $68 million deal in December. He is 3-3 with a 4.08 ERA in parts of two season in Boston. So far this year, the hard-throwing righty has a 6.00 ERA in four starts, allowing 14 runs in 21 innings pitched, striking out 16 and walking 11.
To fill Eovaldi's spot on the active 25-man roster, Boston recalled left-hander Bobby Poyner from Triple-A Pawtucket ahead of Saturday night's road game against the Rays.
In other Red Sox updates, infielder Marco Hernandez, who didn't play last year following left shoulder surgery, is set to start a rehab assignment with Class A Salem. Infielder Brock Holt, out with a scratched right cornea, will meanwhile remain on the injured list after his rehab assignment with Pawtucket.
The Associated Press contributed to this report.