When Chael Sonnen coached Kelvin Gastelum on Season 17 of “The Ultimate Fighter,” he used to pose a question to Gastelum that was often misinterpreted.

Sonnen, a former title challenger at both middleweight and light heavyweight in the UFC, would frequently ask Gastelum, “What are you good at?” when he saw him at practice.

Now, because Gastelum was Sonnen’s final pick that season, his question was often interpreted as a shot at Gastelum’s skills. That, however, is most definitely not what Sonnen meant.

“I’d say to Kelvin all the time, ‘I don’t know what you’re good at,’ which I know sounds like an insult but was meant to be a compliment,” Sonnen told Yahoo Sports. “He was not a great wrestler. He had no jiu-jitsu belt or rank to speak of. He had no striking, at least [not in] formal competitions. But when he got in there, he was just a winner. I would tell him as a joke all the time, ‘I don’t know what you’re good at, but I don’t know how to beat you. If I was coaching against you, I wouldn’t know what to tell the guy.’”

That went on throughout the season. After Gastelum submitted Josh Samman in the semifinals on the last day to advance to the finals against Uriah Hall, some of Sonnen’s other fighters approached him.

And they had an answer.

“It was the very last day and he had just made the finals, and two of the fighters walked up to me and said, ‘We know what Kelvin’s good at,’” Sonnen said. “I stopped what I was doing and I said, ‘OK. What?’ And they just smiled and said, ‘Fighting.’ And that was it. It’s just true. He’s a guy who is greater than the sum of his parts.

“If you took any of the elements and put them into one, if you put him on a wrestling match, hey, look, he’s not winning a gold medal. If he’s on a submission mat, he’s not winning Abu Dhabi. The same thing goes for boxing or kickboxing. But when you put him all together, he’s really something special.”

That ability, to not be special at any one thing but to be good at anything, makes Gastelum a threat to defeat middleweight champion Robert Whittaker on Saturday U.S. time at Rod Laver Stadium in Melbourne, Australia, in the main event of UFC 234.

Gastelum is one of the sport’s most underrated fighters. He’s got a string of notable victories, over the likes of ex-UFC champions Michael Bisping and Johny Hendricks as well as Jacare Souza and Tim Kennedy, among others. He’d have another win over an ex-UFC champion if his impressive 2017 TKO of Vitor Belfort wasn’t overturned because Gastelum had marijuana in his system.

Whittaker is a little better than a 2-1 favorite and will have the home crowd behind him. Gastelum, though, looks at himself as a champion already.

“I came to a realization a few years ago that has really helped me, and it’s that every champion in history felt, or knew, they were the champion even before they had the belt,” Gastelum said. “I realized that the belt is just a consequence of all the work they’d put in. It was the lifestyle they had lived, a champion’s lifestyle, is what made them special. They breathed the champion’s lifestyle; they lived the champion’s lifestyle outside of the Octagon.

“When it came to the fight, they knew because of the life they had lived and the commitment that they’d made that the belt would just be a consequence of it. That’s how I have tried to carry myself. What I do in the Octagon is just a reflection of what I do every day and the time and effort and dedication I put into being the best.”

In many ways, Whittaker is similar to Gastelum, in that he doesn’t have the flashiest tools, but he has a rich résumé with a series of impressive victories. The final two bouts will be all middleweights with the 6-foot Whittaker defending against the 5-9 Gastelum in the main event and the 6-4 rising star Israel Adesanya challenging the legendary 6-2 ex-champion Anderson Silva in the co-main.

The heights show only a fraction of the physical disadvantages that Gastelum faces, but he believes he’s been able to turn his height into an advantage despite giving up many inches.

“I’ve learned to make my disadvantage into an advantage,” Gastelum said. “Guys have a hard time getting up under my hips. If they want to shoot, they have to shoot really, really low and those guys are tall guys. That’s one little example.

“Another is, these guys are used to fighting guys their height. They’re aiming and punching at that range. They’re not used to fighting a guy as short as I am and as small as I am. It throws them off a bit and I’ve noticed that. I’ve learned to make a disadvantage, where some people think I’m too short to be at the top level in this division, be an advantage. It’s worked out pretty well so far.”

It has without a doubt. Sonnen said he learned what makes Gastelum special during his TUF fight with Bubba McDaniel. Sonnen was seated cageside in the TUF Gym as boxing coach Clayton Hires was warming Gastelum up

Gastelum went on to win by second-round submission, and when Hires got a chance to speak with Sonnen, he had a story to tell.

“Kelvin had always been a fun guy, a nice guy to be around, but by no means was he a guy who stood out after a workout,” Sonnen said. “We got back to the house after that fight with Bubba and Coach Clayton said to me, ‘I don’t know that guy I was in the lock room with.’ I was confused and said, ‘What do you mean?’ And he said, ‘Kelvin. The nice, fun guy you see around all the time, that guy was gone; long gone. He was in a zone. He was staring really intently and pacing back and forth and grunting and we just totally left him alone because you couldn’t talk to him.’ The great ones have that ability to flip a switch and become someone else and you know what? Kelvin has that, too.”

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