Six Nations 2016: Ireland v Wales - A great Celtic rivalry

Mike Phillips is on the receiving end of some rough treatment in the 2014 Six Nations meeting with Ireland

It was being billed as the battle between the two men most likely to coach the 2017 British and Irish Lions in New Zealand.

So when Ireland coach Joe Schmidt revealed his contract would not allow him to take a year off to take charge of the tourists, in some people's eyes Sunday's Six Nations match against Wales lost a little of its spice.

It wasn't just a game, it was a presidential candidacy caucus for Schmidt and Wales coach Warren Gatland; the opening round of a campaign which will end in the autumn when the successful candidate will be named.

But wait a second. This is Ireland, chasing an unprecedented third consecutive title against Wales, the side who have so often derailed Irish hopes and, in turn, had their ambitions crushed by the men in emerald.

Celtic cousins, perhaps. Bosom pals - not once the whistle goes. There is no added incentive required.

Ireland and Wales have won six of the last eight tournaments between them and when it comes to sub-plots, there are already enough to populate a season of Quentin Tarantino films.

Here are five of the best.

Grand Slam showdowns

Wales ended a 28-year run without a Grand Slam when they beat Ireland 32-20 at a euphoric Millennium Stadium in 2005.

A day of high drama and higher passion saw plenty of needle.

Brian O'Driscoll had a niggle or two with Gavin Henson, and Gethin Jenkins celebrated Wales' opening try by throwing the ball at Ireland fly-half Ronan O'Gara. He missed.

Four years later Ireland came to Cardiff chasing their first Grand Slam since 1948 and were almost denied when Stephen Jones narrowly missed a long-range penalty with the last kick of the game.

In truth, Ireland's 17-15 win was richly deserved with the peerless O'Driscoll scoring one of their two tries in a dominant second-half display.

But even when clearly the better team, the Irish almost let the cup slip.

Dropping of heroes

Warren Gatland's decision to leave Brian O'Driscoll out of the squad for the British and Irish Lions' decisive third Test against Australia in 2013 caused an wealth of Irish indignation.

In fairness, it was not just in the Emerald Isle that eyebrows and danders were raised.

A succession of former players and pundits rounded on Gatland, who claimed to be shocked at the vitriolic criticism he faced.

Suspicions of Wales squad favouritism were further fuelled because O'Driscoll's omission was to make way for fit-again Jamie Roberts, who was partnered with Wales colleague Jonathan Davies and not O'Driscoll, with whom he'd been such a success in South Africa in 2009.

The fact the Lions crushed the Wallabies to register a first series win since 1997 did little to salve the soreness many felt.

O'Driscoll later the same year said Gatland was unlikely to be on his Christmas card list, but in 2014 had mellowed and said he felt no resentment towards the New Zealander.

Fans are not as understanding.

It's the wrong ball

The match in Cardiff in 2011 was another which left the Irish seething after Mike Phillips scored a runaway try from a quick throw in by Matthew Rees.

It was enough to seal a 19-13 win for Wales - but the try should not have been allowed.

Replays showed a ball boy had handed Rees the ball and that it was different to the one kicked out of play by Ronan O'Gara - both actions against the laws of the game when it comes to a quick throw-in.

"We were robbed," said Ireland skipper Brian O'Driscoll. Though this time it was referee Jonathan Kapland who was the target of his ire, rather than the Welsh players for trying - and succeeding - to pull a fast one.

The Grand Slam that got away

Ireland are the defending champions but 2015 really should have been a Grand Slam year for Schmidt's men.

The fly in the ointment was Wales, whose obstinate refusal to buckle in the face of total Irish domination in Cardiff earned a 23-16 win.

Floodlit robbery? That does no justice to Wales' extraordinary defensive display and the brilliance of Scott Williams' decisive try.

But unquestionably Ireland's lack of the cutting edge they later showed against a less resilient Scotland cost them the ultimate crown.

They tend to meet in big games

Perhaps the simple truth behind the rivalry between Wales and Ireland is that they tend to meet in big matches.

Aside from the Grand Slam showdowns in 2005 and 2009, both teams were unbeaten going into their 2008 meeting in Croke Park, which saw Wales take the Triple Crown on their way to Warren Gatland's first Grand Slam.

In addition, there was the small matter of the quarter final of the 2011 World Cup, when a fancied Irish team were chop-tackled to a comprehensive defeat by a fresh-faced Wales team.

O'Driscoll later confessed that result was the biggest disappointment of his career - and when you consider what happened to him when he was captain of the 2005 British and Irish Lions, that is possibly a surprising admission.

Make no mistake, Ireland versus Wales will lack nothing. This is never going to be friendly.