Jamie Ritchie to miss World Cup opener after breaking cheekbone

However, Townsend said the 12-cap 23-year-old is unlikely to be fit for the showdown with Joe Schmidt's world number one ranked side next Sunday and earmarked the second Pool A clash with Samoa on September 30 for his return.

Ritchie's club-mate Magnus Bradbury, who was called up as a precautionary back-up, remains in Japan for now.

Head coach Townsend, speaking at his official opening press conference ahead of the tournament, said: "Jamie had surgery on Monday so he joined us Thursday. He's still recovering from the operation and also jet lag, so he's not training with us just yet.

"We expect him to resume training next week. He's unlikely to be available for the Ireland game but he will be back in full training after that.

"It was a fractured cheekbone that Jamie suffered. He's got a titanium plate in there now so it's quite a regular surgery for players who suffer that type of injury.

"We believe that two-to-three week turnaround can be done pretty easily. We know some players can come back in less time than that but we're going to aim for the Samoa game rather than Ireland."

Townsend was left sweating on the fitness of five players after that 36-9 triumph over Georgia in the Dark Blues' World Cup send-off.

Ritchie was the most serious concern but there were also worries for Blair Kinghorn and Ben Toolis after both suffered head knocks while forwards Blade Thomson and Jonny Gray limped off with hamstring complaints.

There was further anxiety when prop Allan Dell later reported a hamstring twinge of his own but Townsend admits he is mightily relieved that all of six of his injury doubts are now set to play a part in the tournament.

Townsend – who did lose lock Sam Skinner to a hamstring complaint before naming his 31-man squad – said: "The pleasing thing is everybody is still in the squad, which is a huge boost.

"The last media conference we had (the injuries) were in the front of my mind as we ended up having six injuries against Georgia.

"We had four players who went to hospital that evening and two who had to be removed because of head injuries.

"But all of them are available to play in the World Cup. Jamie won't probably be fit for the first game but the rest are all be available for selection this week.

"That means we're in the best possible condition to play well."

Townsend's team have had to contend with sweltering conditions in Nagasaki, with temperatures in excess of 30 degrees and high humidity levels leaving the players dripping with sweat.

But when they take on Ireland, the forecast is for heavy thunderstorms.

Townsend added: "Nagasaki has been the perfect place for us to get over the jet lag. We're training in the hottest conditions in Japan right now on an excellent training field.

"Conditions will be different next weekend but we're used to the wet. We grew up in Scotland after all.

"We were expecting a wet ball either way. If it was going to be hot and humid like it was in Tokyo last week then it would make for slippery conditions.

"But the forecast is saying it will be wet because of the rain so we've got to have a game based on putting pressure on Ireland, upsetting their rhythm and making sure our strengths are in play.

"We can adapt that to whether it's dry or wet."