In a backroom at Bellmore Kickboxing MMA, Andre Harrison put some pads on the ground and sat down. He worked through a small snack bag as he prepared for his final sparring session of this training camp.

Harrison, from Freeport, thought back to his early days as a mixed martial arts fighter. Before the championship belts. Before his name started showing up in headlines. Before he really knew what he was doing in this sport.

“All my amateur fights were pretty much me writing down workouts that I saw on YouTube,” Harrison said. “I would watch some of my favorite fighters, write down the combinations they would throw and I would just practice those combinations on the bag. [I was] throwing them all wrong, all off balance, but in my mind, I was working out.”

Harrison has come quite far in eight years.

And after four amateur and 16 professional fights — an undefeated resume that includes four promotions and four championships — Harrison begins his reign in the Professional Fighters League, formerly known as the World Series of Fighting.

Harrison won the featherweight belt from Lance Palmer in March and defends it for the first time in the main event on Saturday against Steven Rodriguez at the Xfinity Arena in Everett, Washington. The main card airs on NBCSN at 9 p.m. Rodriguez (10-2), from Costa Rica, is on a nine-fight win streak with four finishes in his last five fights.

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“Every fight has to be better than the last, in my brain,” Harrison, 29, said. “I think about my last performance and what I did wrong, and how I can make that better.”

That may sound like harsh self-criticism for an undefeated four-time champion, with titles won in Ring of Combat and Titan FC as a pro and No Mercy Extreme Fighting as an amateur. But, it helps drive Harrison.

Nearly every fighter says the same thing every time when asked about their goals in MMA: reach the UFC, the sport’s leading promotion. Not Harrison. His answer was more concrete about his goals regardless of the name of the promotion.”

“I want to clear out the division,” Harrison said. “I want everybody in the division to be like, ‘Damn, I’m all right being No. 2.’ I want them to know if they fought me 10 times, they’d lose 11.

“Everywhere I go, I always want to cement myself as being the best. It’s not enough to just get the belt. Anybody can have a good couple fights and get the belt, but I want to cement myself as being the best.”

That work ethic and determination started when Harrison was a youth.

A bet brought Harrison to the wrestling room in seventh grade at J.W. Dodd Middle School in Freeport. If he could last one week in there, coach Dave Gordon would pay him $50.

“Whatever he told those people on the wrestling team, I have no idea, but they beat the heck out of me,” Harrison said. “The week was up, my lip’s all busted up, forehead all mat-burned everywhere.”

Harrison won the bet.

“He was like, ‘You won, you don’t have to come anymore,’ ” Harrison said. “I was like, ‘No, I’m coming. Because I’m going to learn exactly what they know so I can get each and every last one of those dudes back.”

Sure, Gordon lost $50 that day, but that’s a small fee for the chance to set a 12-year-old boy on a course that would help mold his life.

“I knew Andre would be special,” said Gordon, who still talks with Harrison regularly 17 years later. “There are certain kids that have it and certain kids that don’t. Andre, I always knew he would make it.”

Harrison took wrestling a bit further than one week and one bet. He won two Nassau County wrestling titles while at Freeport High School. He then became an All-American for both Nassau CC and Division II Fort Hays State University in Kansas.

That wrestling background has served Harrison well in his MMA career. Eleven of Harrison’s 16 victories have come by decision. But he earned finishes in two of his last four fights.

“A lot of time you get these wrestlers who start knocking people out on their feet, they get comfortable and they get away from what they do best,” trainer Keith Trimble said.

Trimble’s lessons for Harrison are simple as he grows more and more comfortable with the boxing and kicking aspects of MMA: “Just keep people constantly off guard so they don’t know where he’s coming from.”

When Harrison first walked into Trimble’s gym in Bellmore almost seven years ago, Trimble didn’t know where he was coming from either. A friend of a friend of a friend told Harrison to try Bellmore Kickboxing. Harrison had been in Colorado but came home for two weeks to help his mother move home shortly after his brother, Garvey, was killed.

He and Trimble formed an instant connection. Trimble appreciated Harrison’s respectful nature and his lack of attitude or ego. Trimble said Harrison and the other fighters and gym members got along from the start.

“First day I even met him, everything was ‘Yes, sir,’ ‘Hello, sir,’ shake your hand right away,” Trimble said. “When he was leaving, it was ‘Thank you for letting me come into the gym.’ ”

Harrison trained with Trimble every day for those two weeks.

When he returned to Colorado to prepare for his next fight, he called Trimble every day. It didn’t take long before Harrison changed his return flight — the fee paid for by Trimble — and the course of his career.

“He didn’t need me. He still doesn’t,” Harrison said. “I just think generally he’s a good person and just wanted to take a shot at helping me because I needed it.”