So far so good. Scratch that - it's really a case of so far, so brilliant.

Wales' intense 29-25 win against Australia means they top Pool D at the half-way stage and have a 10-day break before facing Fiji on 9 October.

But as the post-match parties pass into memory, coach Warren Gatland has a selection headache to deal with at fly-half.

And for a man whose formidable reputation is built on meticulous planning and ruthless attention to detail, this time the New Zealander might just have his fingers crossed.

Dan Biggar's failed head injury assessment means Wales face an anxious wait to see if they have two number 10s available to play against Fiji.

So, what's the state of play? And what will Gatland do if Biggar is not fit in time?

Background

The Wales number 10 shirt has not been blessed with much luck before and during the World Cup.

Gareth Anscombe and Biggar were in line to be the two specialists in the original 31-man World Cup squad.

But Anscombe was ruled out when he suffered a serious knee injury in the opening warm-up game against England in August.

Rhys Patchell was handed the selection spot in the final squad ahead of Jarrod Evans as Gatland opted to go to Japan with only two specialist number 10s.

Pachell had impressed from the bench against Ireland in Cardiff but suffered a head knock in the return fixture in Dublin and has had his own issues with concussion over the last two seasons.

Wallaby worries

So the last thing Gatland wanted to see during the first half against the Wallabies was Biggar leaving the field and not returning after his try-saving tackle on Australia centre Samu Kerevi.

Replacement Patchell provided a composed 14-point performance to help guide Wales to victory, with his second-half penalty and drop-goal keeping Wales far-enough ahead to ward-off Australia's determined revival.

Wales are waiting to see whether first-choice Biggar proves his fitness before the game with Fiji which could clinch their place in the quarter finals.

Biggar has started his return to play protocols on Monday and could return to training on Friday if he passes all the relevant stages of recovery and tests.

Why the concern?

Biggar's presence is crucial because he and Patchell are the only recognised fly-halves in Wales' 31-man squad.

If the Northampton Saints man doesn't make the cut, then Wales will have to press a non-specialist into action as injury cover for Patchell.

Centre Hadleigh Parkes, who has played 10 for Scarlets, and full-back Liam Williams have been touted as possible cover, but neither are natural 10s.

Williams also picked up an ankle injury against Australia which the Welsh medics are monitoring.

Wales had talked about asking a rookie to cover fly-half for the final group game against Uruguay on 13 October.

But having to do that against Fiji is a different proposition.

Gatland is not alone in hoping Biggar passes his fitness tests - Patchell was full of praise for the former Ospreys man.

"Dan is awesome," Patchell said.

"He takes a lot of heat in the press for whatever reason, but it's only when you are around him on a day-to-day basis you see what an unbelievable competitor he is and how much he wants to win.

"Fair play that was a real act of bravery on our line. He flew into Kerevi. We were thinking that maybe here is a try, and then he comes in with that tackle."

Lock pick issues

The other problem position remains lock, with Ospreys second-rows Bradley Davies and Adam Beard aiming to prove their fitness after not played a part in the tournament so far.

Beard arrived at the World Cup after the rest of the squad after having his appendix removed, while Davies only landed in Japan last week as a replacement for the injured Cory Hill.

Captain Alun Wyn Jones and Jake Ball are the only fit specialist second-rows and have started both victories over Georgia and Australia with Scarlets flanker Aaron Shingler providing the replacements cover.

"It has been very unexpected," said Shingler.

"I'm very happy though to be involved. Coming over here it is great to be involved in the 23 and I'll play any position I can.

"I'm comfortable in that position. I'm more comfortable playing in the back row, but if I have to play in the second row I'll be more than happy to do it."

Eyes on the prize

Injury issues aside, Wales are in a good place.

Firmly in control of Pool D and on course for a potential quarter-final appointment with France or Argentina, if England top Pool C.

The squad arrived in Otsu on Monday from Tokyo, where they will begin preparations for the next stage of their pool campaign later this week.