Have there been any MMA fighters to enter the boxing ring?

[hardcore_crash]

There are many MMA fighters that can box.
Vitali Klitschko,"JDS is a very strong fighter, deserves to be champ, he jabs like my brother Wladimir, so he is learning from the best."

Junior Dos Santos is a great boxer and his boxing has helped him become the HW champ, absolutely outclassing anyone who has stood with him.
He is a really good example of how to use boxing in MMA.

[ElTerribleMorales]

There are many MMA fighters that can box.
Vitali Klitschko,"JDS is a very strong fighter, deserves to be champ, he jabs like my brother Wladimir, so he is learning from the best."

Junior Dos Santos is a great boxer and his boxing has helped him become the HW champ, absolutely outclassing anyone who has stood with him.
He is a really good example of how to use boxing in MMA.

that's not the question at hand though, he's asking if any MMA fighter has ever faced a world class boxer in a boxing match, not in a MMA match, closest thing to come was when there were reports that Diaz was going to fight Lacey or when Silva was going to fight Jones

[hardcore_crash]

I realize that, and I should have quoted Dia.
That's my mistake.

Those two examples you used were very good though.
Diaz didn't end up fighting Lacy because he got the title shot and has "retired" since Condit ran the marathon and testing postive. And in the Silva case, there was no way Dana White was going to let Anderson put his and the UFCs reputation on the line facing a shot Roy and possibly losing. And of course, him not willing to do any kind of co-promotion.

Andrei Arlovski was also getting very serious into his boxing transition.
And there is no doubt in my mind guys like Arlovski and Dos Santos could transition very well in to Pro boxing if they were to focus solely on their boxing.
With Arlovski though, had he not had his problems with his chin he would have by now.
He ruined everything with that flying knee of his, one of the biggest mistake I have ever seen in any combat sport.

[VictorCharlie]

I've always felt Andrei was one of the most physically and technically gifted fighters I've ever seen. His lack of chin has been one of the great let downs in the MMA HW division.

[Beanflicker]

A good professional boxer is too specialized for an MMA guy to compete with him at boxing.

A good MMA guy is too well rounded for a boxer to compete with him in a real fight.

Those are just the facts.

[mattboxingfan]

Freddie Roach's Top 5 Boxers in MMA - Inside MMA - YouTube
Just a video of Freddie Roach's top boxers in mma.

Little Nog was a good amateur boxer he won brazilian championships twice and south american championships.

MMA Ultimate Set: Anderson Silva Sparring at Wild Card Boxing Club - YouTube
Anderson training at wild card