Not just in terms of seeing if the early pacesetters have the appetite for a marathon, or seeing the experienced contenders come through the pack. Or coming through the second international period of the season with something still to play for at the end of it.
There is also the question of being 'man enough' to come through the worst weather of the season.
That goes for supporters as much as players.
We all remember the coldest matchdays, we all talk about them whenever the mercury plummets.
“Absolutely freezing, but not as bad as that day at Newcastle when I lost all sensation” or “Only just got the feeling back in toes and fingers, and it’s now Thursday.”
The cup win over Newcastle Falcons last weekend started cold, got colder, got a bit colder still, and ended in a snow storm which reflected the floodlight illumination and saw the top third of the Caterpillar Stand disappear into the evening sky.
In recent seasons that experience has possibly been rivalled only by the European defeat in Clermont in 2009/10 when The Siberian Tig struggled to even move at the final whistle. The performance of the hosts made the blood run cold in the first half though thankfully the second-half fightback warmed the cockles of the travelling support.
On home soil the coldest must have been that game against Wasps in the same season. The pride of getting the game on – and the winning performance against old rivals – gave us all such a warm glow, though possibly not Lote Tuqiri who may have just regained movement in all limbs and digits.
Exeter away at New Year last year tested the resolve, and the undergarments. And Worcester a couple of seasons ago still brings uncomfortable flashbacks.
Concrete-built stadiums, especially ones where one stand faces the sun and one is sat in the shade from October onwards, provide some of the sternest tests.
The steam rising from players at a scrum is a feature of Sunday newspaper photography at this time of year, every year. The image almost reflects the cold the morning afterwards.
Winter is not the time to be a winger by choice, patiently waiting on the outside, at the mercy of the howling wind and the precipitation. There was a moment last week when Ringo Agulla took the ball over halfway and cut in towards contact – the pass would have meant relinquishing possession he had waited so long for and instead he took to the sanctuary of contact and the heated contest at the breakdown. Who can blame him? It’s a chill wind that blows nobody no good.
But cold days are also significant days in showing the size of the fight in the dog as much as the size of the dog in the fight.
Tiger Tiger burning bright. It doesn’t get much warmer than that.