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Finn Russell led Scotland's epic Six Nations comeback at Twickenham last year

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Influential fly-half Finn Russell will not play in Scotland's Six Nations opener against Ireland next Saturday after "a breach of team protocol", Scottish Rugby has confirmed.

The Scotland players were given permission to have a few drinks when the squad met on Sunday, but Russell is believed to have ignored warnings from management and fellow players to stop.

The Racing 92 fly-half missed training on Monday and was subsequently told by head coach Gregor Townsend he would not be considered for selection in Dublin.

The head coach did invite Russell to return to the squad on Thursday in their preparations for the match, but the player elected to leave the camp.

Russell has declined to comment and it remains unclear whether the 27-year-old will play any part in the campaign.

After last season's epic 38-38 draw with England, Russell said a half-time "argument" with Townsend helped spark a remarkable comeback.

Scotland trailed 31-7 at the break, but roared back to lead before George Ford's last-gasp converted try denied them a first Twickenham win since 1983.

"I actually had an argument with Gregor [at half-time]," Russell told ITV after the game.

"I said to him 'you're telling us to kick and when we kick, they just run it back and cut us open, and when we run it, they're just hitting us behind the gain line and winning the ball back'.

"Second half, we just came out with nothing to lose, played our rugby, kicked out of our half and scored some great tries. We played good Scottish rugby."

'Hard to imagine more devastating blow' - analysis

BBC Scotland rugby reporter Andy Burke

It's hard to imagine a more devastating blow to Scotland's Six Nations hopes just nine days before they kick-off their campaign against Ireland in Dublin.

Russell is the one player in the Townsend's side you would describe as irreplaceable. He's the creative heartbeat of the team and when he's missing Scotland are a much weaker proposition.

His decision to leave the Scotland training camp will send shockwaves through the Scottish support and the Six Nations as a whole.

Townsend was already under enormous pressure going into this championship off the back of a failed World Cup campaign.

Having his star fly-half walk out on the squad just over a week before the Six Nations opener only heaps more heat on the head coach, who must surely be hoping this situation can still be salvaged.