Based on recent history, two things are certain when the Chiefs meet the Blues tonight - there will be 80 minutes of vicious collisions and, in the end, the Chiefs will win.

That much appears preordained ahead of tonight's clash at Eden Park, supported by evidence gleaned from a glut of New Zealand derbies and, in particular, clashes between these teams.

First, the attrition rate these matches take on conference foes has been clear all season and was re-emphasised in the Chiefs' loss to the Crusaders last weekend, with three players forced from the field through concussion.

And with regards to the final result, one compelling statistic seems to suggest it's a done deal - the Chiefs have emerged triumphant from the past 11 meetings between the northern neighbours.

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Faced with those two patterns, though, a deferential Dave Rennie would express his confidence in only one continuing.

The Chiefs coach said about his team's recent dominance over the Blues: "I don't know if there'd be another rivalry in this competition where you'd have a stat like that. But, in the end, it counts for very little.

"[The Blues] are a good side. I know they've lost their other Kiwi derbies but they've been right in them, and in a couple of them they've led all the way.

There's not much between the Kiwi sides so, as we found out last week, you're not going to win every moment but you've got to win the big ones."

Rennie realises there's no avoiding the collisions and, in all likelihood, no avoiding the loss of players to concussion. The Chiefs pair who went off last weekend - Stephen Donald and Sam McNicol - will both miss tonight's match, with Charlie Ngatai making a third player who will be held out as a precaution.

And when the ferocity of modern matches is combined with increasing attention paid to the potential damage of head injuries, it would surprise few if that number grew tonight.

"Bigger, stronger athletes, the ball's in play more and the game's far more brutal, so there's more collisions," Rennie said. "And I think there's far more awareness around it, even with the players.

They're prepared to say, 'I got a bit of a knock and I can't remember this or I'm feeling a bit groggy'. Whereas, probably in my day, you'd fudge it and stay out there.

"There's obviously a lot more common sense in the game, and I think a real willingness from everyone to make sure they don't return till they tick the box. It's a positive stance."