Gore had been dealing with a strained left oblique over the past two weeks, or he may have been called up earlier.
"Because our bullpen is in order right now, we can afford the extra player," Royals manager Ned Yost said. "We were going to do it two weeks ago [when Billy Burns got called up instead], but [Gore] went into the training room that day and said [his oblique] was hurting.
"But now, I don't think there's any danger of reinjuring it."
Gore, who has 17 steals this season in the Minors, said he injured the oblique on a swing.
"Too many swings, I guess," Gore said. "It feels better. It doesn't affect me running at all."
Gore said he, too, had a feeling he was getting the call two weeks ago.
"I said I don't think I can make it," Gore said. "It was aggravating. I couldn't move, even a cough made it hurt. It was a setback for two weeks."
Gore on Friday also recalled his first and only home run as a professional in 2,035 plate appearances earlier this season with Triple-A Omaha.
"It was like I was dreaming," Gore said. "I got around second base [on the home run trot] and it was like, 'This can't be real.'"
Cahill happy to contend Right-hander Trevor Cahill, acquired from San Diego earlier this week, said he didn't get too wrapped up in all the trade rumors. Cahill will make his first Royals start Saturday at Fenway Park.
"I did for a little bit, but then I stopped," Cahill said, who spent the end of 2015 and all of '16 with the Cubs. "I knew [getting traded] was a possibility with the team kind of rebuilding and the Dodgers way out front. It's just nice to be with a contender again, which I was able to do that last two years."
Farewell Farrell The Royals on Friday traded Minor League right-hander Luke Farrell to the Dodgers for cash considerations. Farrell was designated for assignment earlier this week.
Farrell, 26, was 7-4 with a 4.07 ERA in 17 appearances (16 starts) for Omaha.