In the street, in the evening, in front of the casino, in the open air… it seemed last night to locals that Las Vegas had come to Mendoza, and Yésica Marcos, fighting for the first time in her home town and topping the bill, was not about to disappoint. Her Paraguayan opponent, Antonia Ayala "Dynamite" Vázquez’s credentials had led observers to expect that she’d be tough. Claiming a record of seven wins (two by knockout), no losses and one draw, and outweighing Marcos by 300 grams, she came out confidently on the opening bell and claimed the centre of the ring.

Marcos circles her warily, determined not to get caught cold, as she has done sometimes in the past. As the round wears on, she begins to take the initiative with two fast jabs (Antonia backs away swiftly) and a right cross (that she ducks under just in time). Marcos stands back now, knowing it’s not going to be easy. This is no catfight. It’s a duel. Ayala comes forward but seems more hesitant now that she’s seen Marcos’s right, and Marcos resumes the initiative. Two more fast jabs – this time she allows for the backward movement – but Ayala isn’t hurt and responds with a huge right hook (this time it’s Marcos’s turn to duck). She throws the left this time, with less conviction, pre-empting Marcos, who had had the same idea. Further skirmishes. Both women seem adept, with textbook footwork, and well balanced as they throw each punch, but Marcos is markedly the more fleet and restless, taking three steps always to Ayala’s two. There’s more variety, too, in her punching: she’s tried all angles now with her left; but the Paraguayan’s evasive; so far she’s slicing air.

A left-right from the Paraguayan. Then two more. Marcos blocks three of the four punches and dodges the fourth, then gets through with a left as the Paraguayan drops her guard. It pushes her off balance, and the girl from Mendoza gives chase, bouncing lightly as Ayala checks and she moves in. Ayala jabs to fend off the attack but Marcos counters, overtaking Ayala’s left arm as it’s retracting with a fast right cross that strikes her on the temple, bending her sideways. Marcos’s left gets through her guard as the Paraguayan straightens up and turns towards her, and the right goes through the same aperture. A straight left between the eyebrows and right cross that glances off her cheekbone force the Paraguayan to backpedal, and again the Argentinian gives chase, but the Paraguayan checks a second time and counters with a body shot – just inside the hipbone, just legal – as the round ends.

At 32, Vásquez is almost ten years older than Marcos and slightly shorter, but has powerful shoulders and strong arms. She’s in good shape, and in the round break refuses to sit down, but Marcos will make her.

As the Paraguayan comes towards her midway through the next round trying a left to the solar plexus and a right, Marcos throws her left hook, dropping her right shoulder as she does so like a left-arm spinner so that the punch comes in over Ayala’s guard. It’s only a glancing blow because of the angle – one o’clock to seven rather than three to nine – but the Paraguayan seems disoriented and her response is confused: as she draws back her left elbow meaning to throw the hook, she shields from the jab her face with her right forearm but drops it as she reverses the rotation, leaving – for a split second – her face exposed. Marcos accepts the invitation, beating her to the punch with a swift right cross to the chin.

It isn’t thrown with full power – time is of the essence – but it does the trick. Ayala goes limp, she droops, like a scorched flower singed at the stem, before falling back heavily onto her rump. (The way flowers don’t, as Doug Adams would say.) Marcos is already set for the next combination, but her rival is no longer there …

… but at her feet, sitting before her, vanquished, a picture of abjection, arms behind her, legs stretched out, head bowed, like an Oriental under the lash of group criticism; except that with Marcos towering above her, glowering like some Byzantine despot (Racine’s tigress Roxane?), you’d say a slave caught stealing from the seraglio, awaiting sentence, knowing already it will be death.

Her arms and shoulders, strangely, seem more imposing still, envassalled, than they had done free, when she and Marcos stood on equal footing, minutes back, when she had entered the arena, then unbeaten, and like Marcos, plenty eager for the fray.

The ref steps in and motions the Argentinian to a neutral corner. Still looking downward, she obeys. “She knows the blow she has just landed is lethal” reads the caption in Los Andes  “and that Omar Romero’s wasting his breath”.

But he counts all the same, that’s what he’s paid for. Ayala puts her fist to her forehead as though trying to remember his name. Brushes an imaginary lock from eyes in any case closed. Obviously concussed, she turns (with painful slowness, as though moving in treacle, as though straining to prise movement from joints already seized by rigor mortis) onto all fours and essays with moronic deliberation to get up. Placing both fists on the canvas beneath her shoulders, like a sprinter at the starting block, she tries straightening her legs. Her right foot is pointing sideways as though the ankle were twisted. By now the count already has reached nine. But she stands up. And totters backwards. Romero catches her with his right hand, signalling the KO with his left as he does, and she sways and staggers forward drunkenly, feet still at strange angles, legs too far apart. She looks at Marcos, who kisses her gently and shepherds her back to her corner, leaning forward to kiss her trainer (or for a word in his ear - the word you’d exchange, if you’d found a lost child wandering in the street and were returning it, with whichever of its parents opened the door). Then goes back to her corner. Subdued. Not even smiling at this stage.

Ayala totters the last few steps, and turns.

And as she turns, you see it’s sunk in now. She looks broken and may even be crying as her trainer unfastens her gloves. Marcos, reassured now she’ll be OK, intrudes on her grief by saluting her own supporters – de rigeur to do so, surely, when you win by knockout in your home town. But now, amid the celebrations, the defeated fighter is a fly in the champagne. She seems dismayed, aggrieved, indignant – as flies do, I expect, on such occasions – but thinks better of protesting and looks away. Letting the victress “have her moment”, as, the other evening, did Beyoncé.