In the case of Dane Coles, bigger is better. The 27-year-old has long been renowned as the most mobile, agile hooker in the country - a dynamic fourth loose forward-type whose ball skills were best illustrated with his stunning out-of-contact offload in Dublin last year that enabled Ryan Crotty to score the winning try against Ireland.
The All Blacks are never going to turn away dynamic, ball-playing forwards, but their athleticism can't come at the expense of core roles. Coles wasn't failing at the latter in either 2012 or 2013, but the coaches felt he could deliver more and to do that, he would benefit from extra bulk.
At 106kg as he was last year, Coles looked a little schoolboy-esque when confronted at Eden Park by the gargantuan Bismarck du Plessis.
He went okay as it happened in the scrums, but the All Blacks want more than parity at set-piece so Coles was asked to return to Super Rugby in 2014 with more muscle on his frame.
Which he has done. He's now 110kg and with that little bit extra, he's made noticeably more impact in the collisions during Super Rugby.
He has been harder to shift at the breakdown - collecting six turnovers - and has made 105 tackles to be the second most prolific hooker in Super Rugby behind the 109 posted by Stephen Moore.
His new frame suits him well. "I have always been told I was too small," he says. "But if you have got a bit of ticker, hopefully it will take you a long way. But I am at a good weight and I have a bit of confidence in my strength and I know I will have to be at my peak because those English boys are a big and physical and I will have to use every ounce of my strength."
It's not just his physicality that has improved in 2014. Coles has a lineout success rate of 90 per cent - making him one of the leading performers in Super Rugby. There are a few higher, but none of those have tallied 765 minutes of game time.
These improvements in his core role execution have enabled the All Blacks to elevate him to No1 in their pecking order.
"There is always a number of things [that have to be right in the lineout]," he says. "You have got to get the throw straight but if the lift is not right or the jump is not right, you have got timing issues, but unfortunately it always gets blamed on the hooker.
"I have learned to deal with it, but it is a high pressure position. When I was younger and stuffed one up ... you just go into the red. But as you get older you can deal with it a lot better. The best way to deal with it is to move on.
"If you go to the lineout thinking about the last throw that you stuffed up, it will play on your mind a bit. There is a bit of mental skill involved."
Coles in 2014
• 12 games
• 765 minutes
• 105 tackles
• 174 metres gained
• 6 turnovers won
• 88 throws won
• 90 per cent lineout success