One of rugby's most enduring and engaging debates is the coaches' use of the bench.
At its best, a good reserves' bench will add punch and energy to a team; at its worst, the emptying of the bench can look like a cynical exercise in boosting individual player's test caps.
Measuring the effective of the bench can often be a gut-feel thing.
For example, Beauden Barrett has gained a reputation for being a player who can take advantage of tiring defences in a number of positions, while other players are seen as starters who struggle to make an impact off the pine.