BOSTON -- Danny Duffy knew something didn’t feel right.

The starting pitcher was going through his off-day running routine on Monday at Fenway Park when he experienced discomfort in his left leg. It turned out to be a strained left hamstring, which he estimates will sideline him for at least two weeks. The Royals placed him on the 10-day injured list on Tuesday, retroactive to Aug. 4.

“We were running sprints -- it was my day to run -- in the outfield, and [I] felt something and pulled up,” Duffy said Tuesday. “It’s pretty matter-of-fact. I just went over to the training staff and told him, ‘Hey, I think I’ve either got a really bad cramp, or I’ve pulled my hamstring.’ That’s what happened. It’s pretty frustrating.”

Duffy planned to play catch on Tuesday to keep up his arm strength and mobility. He was instructed not to aggravate his injury while doing so.

“Maybe back in the day, I would have tried to prove that I can come back quicker, I can do this faster,” Duffy, 30, said. “But being where I’m at in my career and how long I’ve been around, I know pushing it doesn’t do you any good. I want to do my job every fifth day, but I don’t want to go out there and try to be a hero and make it worse.”

Duffy is 5-6 with a 4.93 ERA in his ninth season. Earlier in the day -- prior to the injury -- he talked about finishing the year on a high note. He was scheduled to make his 19th start of the season on Thursday in the series opener against the Tigers in Detroit. Royals manager Ned Yost expects to use righty Jorge Lopez as a spot starter that day in Duffy’s place.

“He’s up to 75 pitches and probably our smoothest move,” Yost said of Lopez, who threw 54 pitches out of the bullpen on Saturday.

In a corresponding move, the Royals recalled right-hander Jake Newberry from Omaha. He is 2-2 with a 3.86 ERA in Triple-A this season.

“He’s the most experienced right now,” Yost said.

Duffy was frustrated by the injury, but is eyeing a return after following the team’s instructions.

“I’m going to be fine,” he said. “It could be a lot worse. … I prepare super hard to not have these things happen, and my body just didn’t agree with me. I can’t do anything about it.”

What’s in a name?

Over the Aug. 23-25 weekend, players from every team will sport their nicknames on the backs of their jerseys. The third annual Players' Weekend was designed to highlight their personalities and backgrounds.

Cheslor Cuthbert and Hunter Dozier selected new nicknames for this season. After previously wearing “Piri,” a name given to him by his family, Cuthbert chose “Island Boy” this year.

• Every team’s Players’ Weekend nicknames

“I grew up on an island,” Cuthbert, a native of Corn Island, Nicaragua, said. “When I signed [with the Royals] and came over to America, a lot of people said, ‘The little boy from the island just signed.’”

Dozier, who chose “Doz” in 2018, selected a nickname that had previously belonged to his sibling and was passed on to him over the years.

“I have an older brother, so he was kind of ‘The Bulldozier,’” Dozier said. “Once I got drafted, people were saying, ‘You should go by ‘Bulldoz.’ It kind of picked up.”

During Players’ Weekend, the players have the opportunity to design and wear specially-decorated equipment, including spikes, bats and catcher's equipment. Billy Hamilton, nicknamed "Bone," was named the Royals' Players' Weekend Ambassador.