Gallagher (7-0) will make his 135-pound debut on Friday when he meets Ricky Bandejas at Bellator 204 in Sioux Falls, South Dakota.
According to Gallagher, Bellator has promised him a bantamweight title shot at the end of the year in Dublin as long as he's victorious on Friday. That was the main reason for the move in weight class. Up to this point, Gallagher has fought primarily at featherweight.
"I've been promised a shot at the world title in my hometown after I run through this fight, and that's the only reason I went down," Gallagher told ESPN. "But I feel great. I was thinking I would just bounce down to win the belt and bounce back up, but if I keep feeling how I feel now, I'll stick around."
The circumstances regarding Gallagher's potential title shot are unique in that Caldwell is also scheduled to fight at Bellator 204 on Friday -- at 145 pounds.
Caldwell (12-1), who fights out of Alliance MMA in San Diego, said he wanted to challenge himself by fighting up a weight class. Gallagher sees it as a sign the former NCAA national wrestling champion doesn't want to fight at bantamweight anymore.
If that ends up being the case, it's all the same to him.
"If you listen, I say I'm fighting for the belt in December, not that I'm fighting Darrion Caldwell," Gallagher said. "That's a big difference. I am 100 percent down to fight Darrion Caldwell, but I don't care if he's there or not. I'm fighting for the belt in December, it's that simple.
"I don't care who I fight for the world title. They're all running their mouths. They're all talking like they want it. I'm here. And after I win on Friday, I'm showing up in Dublin to fight for the 135-pound belt. Whoever the f--- wants it, let's go. Anyone."
Although Gallagher isn't shy about discussing what's next, he says he's not taking anything for granted after the year he just endured.
The 21-year-old was forced out of two scheduled bouts in the past nine months due to knee and hand injuries. Gallagher admits there were some dark days during that time off, but if everything comes together in the second half of 2018, it will certainly make up for his struggles.
"Every day, when I felt low and said 'F--- this,' I would end the day saying 'I'm going to be a world champion,'" Gallagher said. "When I was able to walk a little further each day and put my own shorts on, those were positive days. When I watched video of my future opponents and took inspiration from it, that was positive.
"I feel great and I came here to do a job. I didn't come here for anything else. I have a job to do on Friday, and I'm going to do it well."