Davies suffered a nasty pectoral injury back in November against South Africa, and has only just returned to light training.
With the first match of this year's tournament against Italy upcoming on Feb. 1, Warren Gatland may have hoped that one of his outstanding young players would be available for selection as Wales begin their defence of the title.
There's no doubting the player's absence will affect Welsh hopes of retaining their Six Nations crown.
Over the last couple of years the youngster has cemented a place at the heart of the Welsh team, and his performances deservedly won him a place in last year's touring British and Irish Lions side.
As Graham Clutton noted for The Telegraph at the time, the decision to play Davies ahead of Ireland legend Brian O'Driscoll for the final Test wasn't without issues. Yet Gatland's decisions (this time as Lions boss) were vindicated according to James Corrigan, again for The Telegraph.
Such performances inevitably attracted the interest of Europe's top rugby sides, and French club Clermont Auvergne moved quickly (per BBC Sport) to secure Davies to their roster from next July onwards.
Sporting director of the French side Jean-Marc Lhermet told reporters just what the Welshman will bring to his side when he said, per the BBC:
His profile fits perfectly to the game that we practise...Despite his young age, he has a huge experience of high-level matches and is one of the world's best players in his position. He will be an asset to our team.
Exactly how much of a miss Davies will be should only be judged after those initial Six Nations games, but clearly he brings a great deal of all-round excellence to an expansive Wales side.
Despite only being on the pitch vs. South Africa for 12 minutes, Davies was still the top ball carrier with 46 metres (per rugbyworld.com).
Wonderfully adept at involving teammates in the pass-and-move philosophy that Gatland likes to instill into his sides, he isn't too shabby either when it comes to the genuine hard graft of the sport.
His 17 successfully completed tackles on the Lions tour was the third best of the entire touring party—per Chris Hewett, Independent—and it's perhaps that penchant for getting stuck in that may be partly to blame for the injury that rules him out this time.