Lions 2013: Wales v England provides ultimate audition
Andy Irvine, the tour manager for this year's British & Irish Lions escapade, observed this week that the last two rounds of Six Nations matches would "go a long way in determining who might, and might not, go" to Australia this summer.
"Selection is going to be extremely difficult because there are so many positions wide open where there are a number of genuine contenders," said the former Scotland full-back.
Since Lions squads are a generally a reflection of the strength of the individual nations at the time, Wales and England - as the two remaining contenders for the Six Nations Championship - are likely to have the largest representations in the party anyway.
Both will probably be into double figures, possibly up to a dozen players from either.
But with so many individual match-ups of Lions contenders running through the teams, Saturday's title decider in Cardiff should have a significant bearing on narrowing down the options for head coach Warren Gatland.
Victory for either side could be the difference in ultimately providing the largest Lions contingent, and perhaps even the captain.
England skipper Chris Robshaw may be the bookies' favourite, but if he comes off second best in the breakdown battle to a revitalised Sam Warburton, or England come up short in their Grand Slam quest, those odds could swiftly change.
Former Wales fly-half Jonathan Davies on Wales v England
“It is like a final trial for Lions selection. It is a massive game for a lot of players”
"Next week is a massive game for Robshaw personally and for the England team," noted former England and Lions coach Sir Clive Woodward.
"Sam Warburton was definitely man of the match for Wales against Scotland, he was fantastic. We've all been looking forward to these match-ups and Lions selection does come down to these big games."
Just a few short weeks ago, Warburton's Lions hopes appeared to be fading fast when he was left on the bench for Wales' trip to Rome. One man-of-the-match performance against Scotland later, and he is right back in the mix, if indeed if he was ever out of it.
"I thought Sam had his best game for a long time," former England and Scotland coach Andy Robinson told BBC Wales' Scrum V programme. "He got his timing spot on the in the tackle contest."
Saturday's match at Murrayfield, dismal as it was in terms of entertainment, did provide some significant pointers towards Lions selection.
As well as Warburton's return to something approaching top form, Wales lock Alun Wyn Jones put in a superb all-round shift of ball-carrying, tackling and set-piece grunt and graft.
With England pair Joe Launchbury and Geoff Parling among the front-runners, and Ian Evans also in the mix, the second-row battle in Cardiff will be another intriguing affair, assuming Parling and Launchbury - who made 16 tackles against Italy - shake off knocks picked up at Twickenham.
Richard Hibbard's contribution to the potency of the Welsh scrum also looks increasingly likely to be rewarded with a Lions place, even if Tom Youngs' dynamism and ball-carrying continues to impress for England.
While England's performance was not one to savour, one player who may have put himself in the Lions reckoning was prop Mako Vunipola, after an impressive first Test start.
"He was a big positive for England. He had a strong carrying game," noted former captain Lawrence Dallaglio approvingly. The off-load off the floor that should have led to an England try when Chris Ashton was tackled short, was just one example of the giant loose-head's nimble handling skills.
Given the horrendous weather in Dublin, any move involving more than a couple of passes came with a health warning, but there were positive signs for some of Ireland's Lions contenders.
In probably his last Test outing on home soil, Brian O'Driscoll operated instead more like a third flanker than the great centre he is - a breakdown bandit winning turnovers and forcing penalties.
While his fitness may be a concern - he was again forced off by injury, only to return to the fray - it was another reminder of his all-round ability.
"He has the quality, he has the past experience, and I think he will go," said three-time Lion and former England centre Jeremy Guscott.
With all the talk of the battle between Leigh Halfpenny and Stuart Hogg in recent weeks, Ireland's Rob Kearney reminded us that he remains a strong contender to join them on the plane.
Jamie Heaslip, the Lions number eight in South Africa, has endured a tough championship, but he too looked more like his old self in a powerful Irish forward display against the French, in the first half at least, while Sean O'Brien's consistent excellence will surely earn him a spot.
Scrum-half Conor Murray, unfortunate to be taken off after an assured outing in tricky conditions, also kept his hopes alive, but his replacement Eoin Reddan - a long shot at best anyway - is out of the equation after breaking his leg in the game's last knockings.
There will no doubt be others who suffer similar misfortune in the coming weeks even before the squad is finalised.
Scotland's Richie Gray, a strong bet for a second-row berth, is to undergo a scan on his injured hamstring, but any significant tear might be enough to remove the blond-haired lock from contention.
But the most significant development for the Lions' hopes of beating Australia did not occur in Edinburgh, Dublin or south-west London this weekend, but Canberra.
The news that star Wallabies flanker David Pocock will miss the series after sustaining a serious knee injury playing for the ACT Brumbies robs the hosts of perhaps their most influential player.