Marcus Kowal will step into a cage for the final time as a fighter Saturday night.

It’s not that the former Strikeforce athlete has lost the love for fighting. Hardly. He’s just too busy right now — trying to change the world.

In 2016, Kowal’s 15-month-old son Liam was tragically killed, struck in his stroller by a drunk driver in Los Angeles. Ever since then, Kowal has dedicated just about every waking moment to making Liam’s life — and his own — count for something greater.

“In my case, I can’t go back in time,” Kowal told MMA Fighting. “I can’t turn back time. I think that’s one of the main reasons why people become very bitter when you lose a child, because you have to move on. You have to move forward. I can’t get my son back. But what I can do is make sure that my son doesn’t become a statistic. That because of my son, there’s a chance.”

‘I can’t get my son back. But what I can do is make sure that my son doesn’t become a statistic.’ -Kowal

Kowal, 40, will fight Saturday night at California Xtreme Fighting at the Sportsmen’s Lodge in the Studio City neighborhood of LA against Benji Gomez. The retirement bout is working for him in two ways: for closure and to draw some attention to the causes very dear to him.

Once the weight cut and the fight are over, Kowal will hit the ground running again. His book, “Liam: A Moment on Earth,” will soon be published in English after the first edition came out in Kowal’s native Swedish. Kowal’s plan is to grow his non-profit organization, Liam’s Life, even more in 2018. And this year, Kowal will work with the California Highway Patrol and speak to students in 57 high schools about the dangers of drunk driving.

“A lot of times when I go out to these high schools the kids think it’s cool that I’m a fighter,” Kowal said. “I think my message gets through to them a little more.”

Oh, and by the way, Kowal is also the owner of the Systems Training Center gym, which now has four locations in the Los Angeles area. He coaches fighters he expects to be in the UFC soon enough. Meanwhile, a documentary crew has been following him around for nearly a year, so closely that they were in the delivery room for the birth of Nico, Liam’s younger brother, six months ago.

Kowal is staying active and keeping his plate incredibly full, because he believes he has to. It’s his calling now. Kowal said many parents who lose children turn to alcohol and drugs to cope. He needs to find another way to carry on. Kowal said he began writing the book — which he calls a “love story between a father and his child” — four days after Liam’s death.

“It’s not something I condone, but I understand it,” Kowal said of how others deal with substance abuse. “Because the pain is so immense that you almost become desperate to find a way to numb that pain. The book is about grief and how do you move on. How do you find a way back to happiness again? Dealing with grief is very subjective. At the same time, I feel like there’s certain things you have to do and do in a certain way. I think we’ve dealt with it in as healthy a way as we can.”

Kowal is devoting a lot of time and energy to fighting for drunk-driving reform. He wants to reduce the legal blood-alcohol limit from 0.08 to 0.05 or even less. The 72-year-old woman, Donna Marie Higgins, who struck and killed Liam with her car was convicted of vehicular manslaughter last August and sentenced to six years in prison.

Kowal said he has already met with the team of California Lieutenant Gov. Gavin Newsom, a gubernatorial favorite later this year, about changing the law. And there is more to do.

“I live in the U.S. for a reason,” said Kowal, Swedish immigrant. “I love the country and that’s why I’m here. But just because you’re the best country in the world doesn’t mean … just like for a fighter, jut because you’re the best in the world doesn’t mean you don’t have areas to work on. When it comes to drunk driving, the United States is ranked third in the world when it comes to deaths.

“The truth of the matter is that it’s because of lobbyists. It’s a false perception that if we lower the drunk-driving limit, then the alcohol industry, the restaurant organizations and the nightclub industry would lose money. It’s not true.”

Kowal has picked CXF as the promotion for his final fight, because of what the organization did after Liam’s death. CXF gave a portion of the proceeds from ticket sales and T-shirts at its September 2016 show to Kowal’s family. Liam’s Life, Kowal’s non-profit, is written on the top of CXF’s cage. All this happened without Kowal’s knowledge.

“They didn’t do it for ticket sales, they didn’t do it for media,” he said. “They didn’t even tell me. I found out through friends. … I train with some of the best in the world. I know where I’m at, level wise. And I wanted to say goodbye to the sport and it felt right to do it with CXF, because they did so much for my son.”

The time was now to end his fighting career, Kowal said, because he wants to focus on coaching and the other important things going on in his life. He turned pro as a kickboxer at 23 years old and has more than 50 fights under his belt in boxing and kickboxing. Kowal is just 3-1-1 in MMA going back to 2009 and feels he could have done more in the sport, but he’s comfortable with where things will end. Saturday night will give him closure.

“You can’t be a good coach and a good fighter a the same time,” Kowal said. “You have to pick one.”

Kowal is many things to many different people. To himself, he’s still a grieving father, but one who can make a difference with an uncanny will. Kowal said there’s “no counterargument” as to why people are allowed to get behind the wheel after drinking. And he’s going to make sure his voice — and his story — gets heard.

“I’m a pretty driven person anyway,” he said, “but that’s why I know I will succeed, because I won’t stop until we get there.”