Manager Buck Showalter said Trumbo would have an MRI on Tuesday morning to determine the extent of the injury, which he was concerned could be an oblique strain.
Trumbo called it only an upper body injury Monday.
“With this type of injury, you get a pretty good idea of what you're dealing with,” Showalter said.
After the game, Showalter added more clarity to the situation.
“We’re hoping that it’s eight more days,” he said, as Trumbo was placed on the disabled list retroactive to Sunday. “It felt like it was going to be four or five days before he could test it, and then feel comfortable about him doing it, so you’re talking about six or seven [days] there, then a couple days, so it’s 10. I’m hoping it’s eight more days, but those things are so unpredictable. It’s hard to tell.”
The club's need to activate new pitcher Jeremy Hellickson meant putting Trumbo on the disabled list before further tests were administered.
Trumbo had started every game of the season before Sunday, when he was doing squats to stretch in the weight room before the game at Globe Life Park in Arlington, Texas, and tweaked his back.
He was scratched from the lineup and also was left out of Monday's lineup against the Kansas City Royals.
Trumbo, the reigning major league home run king, is having a down year by those standards, hitting the DL batting .238/.300/.405 with 17 home runs and 50 RBIs.
Hellickson, who was acquired Friday night from the Philadelphia Phillies, had to be activated by Monday. To make room for him on the 40-man roster, the Orioles transferred shortstop J.J. Hardy (fractured wrist) to the 60-day disabled list. Hardy cannot be activated until Aug. 18, though it's unclear whether he would be back by then anyway.
Yefry Ramírez added: The Orioles' first piece of business Monday before the nonwaiver trade deadline was to add minor league pitcher Yefry Ramírez from the New York Yankees for international signing bonus slots.
Ramírez, 23, was 10-3 with a 3.41 ERA for Double-A Trenton, and executive vice president Dan Duquette said he was having a "really good year."
"We like him as a future candidate to help in our rotation," Duquette said.
"Got a good arm," Showalter said. "A good addition."
Ramírez, who is on the 40-man roster and was assigned to Double-A Bowie, has a fastball that sits 91-95 mph and a feel for a slider to go with a developing changeup.
The Orioles have traded several international signing slots for more developed pitching as opposed to using them in the international market.
Around the horn: Former Orioles pitcher Jeremy Guthrie retired Monday. He announced the decision in an article for The Players’ Tribune. Guthrie pitched for the Orioles from 2007-11, and was the team’s Opening Day starter three times in that span.