Every successful boxer has their defining fight: the one in which they announce their emergence out of a slew of rival pretenders as a champion - or even a superstar - in waiting.

Some come early - an undercard win so emphatic it pricks the ears of the promoters and pay-per-view bosses who will then cosset and protect their ace performer with a view to big fights further down the line.

Others occur to announce a fighter's arrival at the peak - Ricky Hatton cut a swathe through WBU title pretenders but it was the night of his epic win over Kostya Tszyu which finally sent him hurtling to global fame.

Amir Khan's defining fight is not on Saturday night. For all the undoubted qualities of his opponent, Dimitry Salita, it is not the contest in which we will establish whether Khan can really cut it as a future Las Vegas bill-topper.

Khan could hardly have hand-picked a better first defence of his WBA title - but even the Bolton man will admit Salita is hardly cut from the same cloth as rival 147lbs fighters like Timothy Bradley, Nate Campbell or Juan Diaz.

Further down the Newcastle bill is, however, one such fight: a mouth-watering affair featuring Khan's former one-round conqueror Breidis Prescott and the long-time next big thing, Kevin Mitchell.

Mitchell, once seen as a genuine rival to Khan, has remained unbeaten but somewhat lost momentum, with two low-key wins over journeymen opponents all he has to show for what he hoped would be a breakthrough 2009.

Suddenly, with the turning-pro of Olympic gold medallist James DeGale and his Beijing team-mates Frankie Gavin and Billy Joe Saunders, there is a sense Mitchell has been shunted out of the headline slot.

Mitchell, 25, desperately needs that big test to catapult him back into the nation's consciousness, and there could hardly be a better - or indeed more daring - foe to face than the big-punching Prescott.

For Prescott himself, the fight also represents a cross-roads. Having beaten Khan and won by disqualification over Humberto Toledo, Prescott blew his big chance of a Khan rematch by losing a split decision to Miguel Vazquez last time out.

The Colombian knows just how much Khan's defeat still rankles with the Bolton team, and how much there is a desire from all parties and in particular from boxing fans to see a big-money rematch.

An emphatic victory over Mitchell would almost certainly pave the way for that fight to happen - and such would be the hype surrounding it that it could even prove to be the occasion of Khan's projected Las Vegas debut.

For Mitchell, however, the rewards promise to be equally huge, with a victory over the man who destroyed Khan suddenly lifting the Dagenham man from Bethnal Green bill-toppers to the verge of a WBA title shot.

The public clamour for Khan-Mitchell would surpass even that for Khan-Prescott II - and the pair have already been talking up the possibility during the hype and bluster of fight week.

"Amir was made out to be a superstar so when Prescott came over and demolished him it made him (Prescott) look a world beater," said Mitchell.

"But I fancy demolishing Prescott within 10 rounds. Then I'll be the superstar."

It is also one of the cleverest fights put on a by promoter this year: not only does promoter Frank Warren evidently believe it's time for Mitchell to cut the mustard, but he guarantees a bona-fide domestic super-fight if he does.

If Prescott returns to the form he showed for all of 54 seconds against Khan, and brings a crashing end to Mitchell's unbeaten record, then the big rematch will await and Mitchell will be left out on the cold.

So it's Mitchell's defining fight, all right. How he looks back on his boxing career in years to come is likely to be defined by events in Newcastle on Saturday night.

It's the kind of fight worth paying the ticket price for alone.