David Flatman: Men to watch for big hits and giggles

Chris Ashton (England)

This one is more about watching the defences facing him than the man himself. We've seen how the Saints winger poaches, pops up and pounces, terrifying exhausted front-five players around the world. What will be interesting, though, is whether the opposing gorillas have done their homework. If they haven't, they will pay, and he will be swan diving for fun.

Fabien Barcella (France)

The French loosehead prop took the world by storm two years ago, by tearing the All Blacks scrummage to pieces almost singlehandedly. Then his Achilles' tendon went pop. Since then he has played virtually no rugby but he has been named in his national squad anyway. He is incredibly powerful and massively aggressive and Marc Lièvremont must think he's ready. It's worth assuming, too, that there will be just a dab of pent-up aggression that needs releasing. I'd love to see England's Dan Cole dish him up in the quarter-finals.

Stephen Ferris (Ireland)

Of all the guys I have played against in the last few years, Ferris makes rugby look the most hilariously easy. Certainly, he will face a battle for his jersey in the Irish side, with Sean O'Brien in dominant form, but still, the Ulster flanker is surely too good to leave out – and David Wallace's sad injury probably leaves a slot open. Just watch how big and strong he looks, even on the world stage. Put simply, when fit, the man is a freak. And yes, I am jealous.

James O'Connor (Australia)

We played against this winger last summer, when he ran out for the Australia A team. We were warned about his dancing feet and turn of pace but assumed we'd seen his like before. We were wrong. They dragged him off after just 50 minutes in the end, primarily to preserve him for the Test three days later. By the time he loosened his laces he'd scored three incredible tries, battered most of our team and managed to make a lot of very good players look very average. Everyone knows he's sharp, but nobody knows his power and drive until they try to stop him. A phenomenon, he could well be the best player in this tournament.

Conrad Smith (New Zealand)

Forget the hype, Smith is the best centre in New Zealand. He probably doesn't hit as hard or offload as readily as does Sonny Bill Williams, but his intelligence and guile make him, if anything, even more of a threat. He isn't hugely quick, nor is he worryingly strong, but somehow he just knows the game and sees things before they happen. Like Will Greenwood, Smith is an arch manipulator of defences who seems to make very few mistakes. He might not have the guns of Ma'a Nonu, but all the biceps curls in the world don't get you through a gap.

Adam Jones (Wales)

Nobody goes about his business with greater effect and less noise than the Ospreys tighthead. As all good props should aspire to be, he is a begrudging hero. You won't see him making breaks or offloading out the back but trust me, if Wales have any hopes of success in the next few weeks, Jones has to be fit. Without him they will not compete at the same level. His experience, technique and sheer ape strength bring a solidity and threat to the Welsh set piece that dies in his absence. You'll just have to excuse the haircut – it's fashionable over there...

Bakkies Botha (South Africa)

Bryan Habana provides the box-office appeal to this Springbok side, but to do this he needs to have the ball. Through an effective mixture of skill and raw aggression, Botha sees to it that not much ball gets taken off the Boks. With the retirement of the England lock Danny Grewcock, Botha became perhaps the last of a dying breed: the rugby enforcer. Plenty talk about it, but he delivers. Sometimes – in fact, quite often – he oversteps the mark and finds himself in trouble but, while we don't wish to condone mindless violence at any level, the threat of him arriving with an elbow, knee or size 14 boot as his opponent tries to pilfer the breakdown seems to work. Hard as nails. Harder, probably.

Mamuka Gorgodze (Georgia)

I watch a lot of French Top 14 games and, as far as I'm concerned Gorgodze, the Georgian back-rower known, predictably, as "Gorgodzilla", is the best player currently playing in France. The bloke is a monster and were he English or French he would by now be a superstar of the game. Destructive, quick, skilful, combative and with an unearthly engine, it's just a shame Georgia won't make it past the group stages. He's incredible to watch.

Manu Tuilagi (England)

I couldn't leave him out, I just want to see him getting quick ball in the first five minutes against Argentina. Given a bit of time and a metre or two of space he will become a mobile nightmare. We know how physically blessed he is and how hard he fights, but I'm keen to see him defend against a top-class attack as they try to use his bulk and commitment against him. Most of all, though, I want to see somebody run straight into him and get knocked into next week. Is that wrong?