Check out two of the pound-for-pound best fighters in their own sports, former UFC bantamweight champ TJ Dillashaw and junior lightweight titlist Vasyl Lomchenko, square off in sparring session and discuss who would win in a Mayweather-McGregor fight. (1:37)

Editor's note: This story was originally published on March 28.

OXNARD, California -- While a proposed boxing match between Floyd Mayweather and Conor McGregor would certainly promise a (lucrative) show, opinions differ on whether it would produce anything that actually resembles a compelling fight.

As the combat sports world speculates over that matchup, a different chapter in boxing vs. MMA took place recently just off the California coastline.

Junior lightweight world titleholder and two-time Olympic gold medalist Vasyl Lomachenko (7-1, 5 KOs) and former UFC bantamweight champion TJ Dillashaw (14-3) sparred for four, four-minute rounds last week inside World Boxing Gymnasium.

It was a marquee matchup to say the least. ESPN.com currently ranks Lomachenko and Dillashaw the No. 3 pound-for-pound fighters in their respective sports.

Brett Okamoto

The sparring session was not for the sake of show -- or money. It happened because both athletes felt it would be fun and, for Dillashaw, beneficial.

"I need to learn what's up," said Dillashaw, before stepping into the ring. "I'm always trying to expand my knowledge as a mixed martial artist. I'm such a big fan [of Lomachenko], I wouldn't pass this opportunity up. Even if I get obliterated, it's something I'll remember forever."

After four rounds, it was abundantly clear that Dillashaw had lost.

In his defense, it wasn't a fair fight. In addition to enjoying the very obvious advantage of it being a boxing match, Lomachenko was in superb shape. He fights Jason Sosa next Saturday in Oxon Hill, Maryland. Dillashaw isn't expected to fight until July, and he was visibly fatigued after the first round.

Afterwards, when asked if he felt he could have landed anything he wanted at any time, Lomachenko confidently responded, "Yes, I feel that. Yeah."

He also gave Dillashaw credit, however, particularly for a few shots landed in the opening four minutes. About midway through the first round, Dillashaw swung over the top of Lomachenko's head with a left hook, then pivoted to his left and connected a flush straight right to the chin.

"I don't like, he punch my head a couple times," said Lomachenko, who is from Ukraine. "When we start sparring, I started a little bit relaxed, little bit not serious. Then he punch a couple times in my head, I think, 'Oh, OK. Let's go.'"

Both Lomachenko and Dillashaw said they want to see the Mayweather vs. McGregor fight come together, as it will be good for both sports.

As far as what tactics McGregor (19-3) may use to level the playing field against Mayweather (49-0, 26 KOs), arguably the greatest boxer of his era, Dillashaw pointed to his size advantage, but not much else. He didn't seem to think an MMA fighter could "trick" his way into being competitive in boxing.

"If you're only using your hands, the distance is a lot closer, and the pressure is a lot different," Dillashaw said. "I can keep someone off with a takedown because they're stalking me or use kicks to keep them at a better distance. In boxing, you don't have to worry about those things so it's a different pace.

"[Conor] would use his size. He's a lot bigger than Mayweather. If he can keep his distance and land that big straight left, that's his only real shot. Other than that, Floyd's defense is too good, and the distance he'll use is so different than what Conor is used to."

Lomachenko's take on the fight was quite direct.

When asked if McGregor could win just once if he fought Mayweather 1,000 times, Lomachenko responded, "I think no. I think Mayweather win. Every day, every time."