They are the nights they look unbeatable.

Muhammad Ali’s performance against Cleveland Williams is often recalled this way.  Mike Tyson-Michael Spinks is as well. 

We know no one is really unbeatable.  Occasionally, the rare fighter makes it to the finish without a loss but that’s just fortune.  Ali and Tyson lost.  Klitschko, though it’s been awhile, has been beaten.  He probably will be again before he hangs them up.

The pursuit of his crown is more interesting when there are opponents who come to fight.  Pulev did.  The winner of this weekend’s big Heavyweight fight would.

As a bonus, they’d make the build to any challenge worth every sound bite.

Saturday in London (ESPN3.com, 5 PM EST/2 PM PST), consensus top ten Heavyweights Tyson Fury (22-0, 16 KO) and Dereck Chisora (20-4, 13 KO) lock horns for the second time.  The stakes are high.  The winner of this WBO eliminator will presumably be a mandatory for Klitschko sometime in 2015.

The fans win no matter which of the fighters does.

Fury and Chisora bring several appealing components to the table.  They talk a big game, both come to fight, and each can punch enough to make a sudden exit possible against anyone.  Their first fight, while one-sided for Fury on the scorecards, was fun.  Chisora didn’t give himself the best chance to win.  He showed up a ghastly 261 lbs.

Fury, a 6’9 volume puncher with power, made him pay.  Standing roughly eight inches taller than Chisora, he came in lighter at 255.  Fury kept his work rate up and outworked Chisora almost bell to bell.  Chisora still had his moments.  Those moments make this rematch must-see. 

It is a question of condition. 

Chisora has been below 240 lbs. for each of his last three fights.  He’s won five in a row since losing three straight, four of those wins by knockout.  The losses weren’t all bad either.  He was robbed against Robert Helenius and gave Vitali Klitschko a spirited losing effort for the WBC Heavyweight belt.  A big UK showdown with David Haye was the worst of the lot, Chisora stopped in five and overwhelmed by Haye’s speed and athleticism.

Fury is the toughest foe he’s seen since Haye.  If he can win here, he turns a professional corner and proves a contender again.  There are many who like Chisora’s chances.

Fury has skeptics. 

He was dropped and badly hurt by former Cruiserweight titlist Steve Cunningham before scoring a knockout in his lone 2013 outing.  Fury ballooned to 274 for his lone fight in 2014.  He’ll have to be in better shape this weekend if Chisora maintains his recent trend of dedication.

Expect a much lower scale record than 274 this weekend.

When it’s over, we’ll have an idea of at least one challenger for Klitschko next year.  Both men have the personality to keep the Pulev chip on his shoulder.

If Chisora wins, there is history and built-in animosity.  Chisora was slated to challenge Wladimir years ago but it fell apart due to injury and the Klitschko-Haye Superfight came together.  Chisora made hay about that in the build to his fight with Vitali and a good ol’ fashioned boxing circus ensued.  Chisora talked an insane amount of trash.  He smacked Vitali at the weigh-in.

And, in a clip ready-made to be played 1000 times in any pre-fight hype, he spit water in Wladimir’s face in the ring before the opening bell of the Vitali fight. 

Any good promoter wouldn’t let that be forgotten.

Chisora would probably take pride in it while the tickets were being sold. 

Heavyweight grudge matches are always welcome.  Chisora challenging Klitschko would supply. 

Fury has talked down Klitschko plenty already.  If there isn’t a legitimate grudge yet, there would be by the opening bell.  Fury is one of the best talkers at Heavyweight since Ali.  Eloquent and tacky at the same time, Fury knows how to sell a fight. 

Klitschko has seen a little bit of everything in his current reign.  He’s seen size, some guys who can punch, guys who come to survive, and foes that can box.  We haven’t seen him much with men considerably taller.  Fury is the one at least semi-proven contender who would look down on the champion. 

None of this is to say that Fury or Chisora could beat Klitschko.  It’s unlikely.  What they bring to the table is elemental.

They can make people want to see if they can win.

They can sell to fans wishing to see Klitschko shut them up.

They can give boxing lovers another fight to talk about, and look forward to, for the Heavyweight Championship of the World. 

On the heels of Klitschko-Pulev, that’s a win no matter what.

Cliff Rold is the Managing Editor of BoxingScene, a founding member of the Transnational Boxing Rankings Board, and a member of the Boxing Writers Association of America.  He can be reached at roldboxing@hotmail.com