Sometimes you watch a fight and you get the sense that the boxer who is winning is just one punch away from losing. I had that feeling about Daniel Santos almost all the way through his fight with the long-serving Mexican, Yory Boy Campas, at Bally's casino hotel in Las Vegas on 16 March.
Santos won, in the 11th round, to capture the World Boxing Organisation junior middleweight title vacated by Harry Simon.
But I am sure that there are a lot of boxers in the 11st (154lbs) division who will fancy their chances very strongly indeed against the Puerto Rican. Any one of Britain's big five light-middleweights - Richard Williams, Wayne Alexander, Steve Roberts, Takaloo and Gary Lockett could, I think, beat him although Lockett will probably require a bit more experience.
It's not that Santos is totally lacking in talent. He can box quite cleverly and he hits hard with the left hand out of the southpaw stance, even though he tends to club with it rather than punching straight.
The problem with Santos, though, is his chin. British fans saw this when Santos was dropped in the first round by Neil Sinclair at Sheffield although he came back to win in the second.
In one of Santos's two defeats he was drilled in the fifth round by Kofi Jantuah, a fighter from Ghana who now lives in Las Vegas.
And against Campas, who is slow, hittable but heavy-handed, the Puerto Rican had some shaky moments - and one downright perilous passage, in the eighth round.
It was only in the 10th round, when he split Campas's right eyebrow with a big left-hander, that I felt reasonably certain that the 26-year-old was going to come out on top against the 30-year-old former International Boxing Federation champ.
In the 11th, a bloodied Campas signalled he could not continue, and referee Joe Cortez stopped the fight, after one minute, 36 seconds of the round.
But that eighth round had been one of near-catastrophe for Santos. His promoter, Ricardo Maldonado, told me afterwards: 'Yes, we were very worried in the corner. We told him to box, to keep moving, not to trade punches.'
Santos looked so shaky in the eighth - first when hit by a left hook, then when a right-hander nailed him - that Campas seemed on the brink of one of those thrilling, come-from-behind victories. But the veteran of 83 fights (67 KOs, and only four losses) just could not land the one more direct hit that might have done the job for him. And give Santos credit for this: although in deep trouble he had the basic instincts to move, grab and throw punches back.
The younger man's recuperative powers were good enough to allow him to get over the immediate crisis, although he still did not seem fully recovered in the ninth and wilted a bit when Campas dug in some left hooks on the inside.
But - and again credit where it's due - he pulled himself together in the 10th, dug in his heels and fired the left hand that brought blood spurting from above Campas's right eye and a look of discouragement to the well-battered features of the old warrior.
Santos followed up fiercely in the 11th and Campas now had no great desire to continue. We have seen it before from Campas, in fights with fellow-Mexican Jose Luis Lopez, Fernando Vargas and Oba Carr, when he gives up after getting cut. This time I could not blame him. He said the blood was getting into his eye and he couldn't see. Santos made a taunting gesture and said something to him.
Afterwards, Santos, who speaks quite good English, said that he didn't want the fight to end the way it did, with his opponent walking away from him. 'It wasn't a good way for the fight to end,' he said.
In other words, with Campas on the way out, he wanted the chance to knock him out.
The victory makes Santos a two-time WBO champ, having held the welterweight title before moving up in weight. 'I proved I can box, fight and hit,' he said. 'Campas hits very hard but I thank God my recuperation is very good.'
Well, it was in this fight - but Campas didn't have the quickness to follow up.
Even in the early rounds, when his moves had Campas looking clumsy, Santos had a vulnerable look. The Mexican faction in the crowd booed Santos for hitting and running and chanted 'May-hee-co.' But in the fourth he stood his ground and landed some heavy left-handers that had Campas looking a bit unsteady. One judge made this a 10-8 round for Santos even though he did not knock Campas down. But, by staying in one place to unload big punches, Santos was putting himself in a position where Campas could hit him, and that wasn't a good idea at all, as we saw in the fifth round when a right-hander had Santos looking a bit unsteady.
Santos was fine when he moved and jabbed but every time he was on the ropes or backed into a corner it was heart-in-mouth time for his anxious handlers. The fight was balanced on a knife's edge in the eighth, that's how close Santos looked to losing even though this was the only round that Campas won unanimously on the judges' cards. After 10 rounds Santos was leading by scores of 99-90, 99-91 again and 97-93 but if you were in his corner I doubt if you could relax until it was over - indeed there was yet another anxious moment for Team Santos even in the 11th when the Puerto Rican turned away and put a glove to his jaw: he said afterwards that Campas had elbowed him. But by now Campas was a spent force and looking for the exit.
If Santos-Campas disappointed the aficionados, the other title fight on this show lived up to promoter Bob Arum's billing of 'Latin Fury' as the lanky, moustached Antonio Margarito stood up to some early-round blasts and came back to outpunch and overwhelm Antonio Diaz in the 10th round to capture the vacant WBO welter championship.
The all-Mexico war (although Diaz was raised in southern California's Coachella Valley) was bruising and thrilling.
Diaz is only 25 but he's had a lot of hard fights, including a brutal victory over another Mexican, Hector Quinones, not to mention getting beaten up in six rounds by Shane Mosley.
The recently wed Diaz (his glamorous wife was at ringside, looking distraught as the rounds went by) had his career at stake. His manager, Lee Espinoza, told him before the fight that if he couldn't win he should think about retirement. 'He's got his life ahead of him,' Espinoza said. 'He's bought himself a jewellery store, he's married now, and this is a tough business.'
The manager does not want Diaz to become simply an opponent. But fighters find it hard to quit.
Diaz showed his great fighting heart, always prepared to go toe-to-toe, and for six rounds the fight was level on the scorecards. But the 23-year-old Margarito, from the border city of Tijuana, took charge from the seventh before Diaz went down on one knee in the 10th, when it seemed that his physical and mental reserves just collapsed.
Even though there had been some bitterly contested rounds - and Margarito showed a great chin to shake off some jarring blows - from ringside you could see the energy slowly ebbing from Diaz the longer it went.
There is nothing fancy about Margarito but he keeps throwing right hands, left hooks, uppercuts, and he isn't always right in front of the other man: sometimes he moves and sticks out the jab. But he always seems to be doing something, including switching to a southpaw style (and flicking out the occasional back-hander, for which he was cautioned).
Diaz took a hammering in the seventh but shook his head in the 'nothing' gesture. By the ninth Diaz was swollen around the eyes and the right eye was closing. In the 10th he finally caved in, taking a knee after being hurt by uppercuts. He got up at the eight, blood inside the mouth, and was taking punches on the ropes when his corner threw in the towel and referee Jay Nady called a halt - not a moment too soon - after two minutes, 17 seconds of the round.
This was a huge win for the little-known Margarito, whose previous challenge for the title was the disappointing no contest with Daniel Santos when the Mexican fighter was horribly cut in a first-round clash of heads. But this made up for it.
Afterwards, Margarito said his biggest concern was Diaz's greater big-fight experience. 'But, little by little, I started to break him down,' he said through an interpreter.
After nine rounds Margarito was in front by scores of 87-84, 87-84 again and 86-85. It was clear from the midway mark that Diaz was going to have to outlast him to win - and equally clear that Margarito was the man with the greater reserves.