The opening encounter between the hosts, France, and three time winners and perennial contenders, New Zealand, did not disappoint. After some typically cagey opening  kick ping pong they were sliced open by New Zealand in the prelude to Beauden Barrett's cross-field Kick for Mark Telea to score the fastest opening try in World Cup history. After that the superior French pack gradually wore NZ down, helped by vociferous crowd support and 13-5 penalty count in the favour.

France showed that even with injuries to key players, they are going to be extremely difficult to beat at home. South Africa know they can beat  the All Blacks. They'll not be so sure about beating France on this form. The Ireland South Africa game just got even bigger as it may determine who gets to play France in the quarter final.

Ireland played reasonably well to beat Romania, one of the weakest teams in the competition, by a record 82-8 score, despite conceding an early try. Ireland will need to work on their lineouts and mauls - a recent problem, but otherwise the game provided good game time for those who needed it. There were some good angles of running, offloading, passing and interplay between backs and forwards and lots of good conditioning in extreme heat. Most of all, there were no serious injuries. A great start to our competition.

Australia surprisingly beasted Georgia up front, a weakness in recent Australian teams and a traditional strength of the Georgian game. With a relatively easy draw, they may yet make the Semi-finals with the experienced but often controversial Eddie Jones at the helm despite this being only their first win in 6 games under his stewardship.

I had Argentina marginal favourites to beat an out-of-sorts England team after they had beaten Australia away in the Rugby Championship and been reasonably competitive against New Zealand and South Africa. How they managed to lose to a 14 man England team, again losing a player to a red card early in the match, is beyond me and counts as an upset in my book.

Fair dues to an England pack which made light of the numerical deficit to dominate Argentina up front and to George Ford showing extraordinary leadership and accuracy with the boot to register a convincing win. What happens to the suspended English Captain, Owen Farrell, now? Whatever else, this England team will be hard to beat, even if they play a rather conservative, old school, bad weather, brand of rugby with lots of long range kicking.

When combined with Wales's creditable performance in beating a strong Fijian side, Italy hammering Namibia, Scotland being competitive against South Africa, and France beating New Zealand, it puts Ireland's Grand Slam win into a very positive perspective. England are the only Northern Hemisphere side to have won the World Cup in nine attempts, but so far, European sides have given a good account of themselves.

Fiji can count themselves unlucky to have lost, having lost the ball twice over the try line and once, in the final moment, when star payer Radradra knocked the ball on with the line at his mercy.  Referee Mathew Carley also seemed very lenient towards repeated Welsh offences close to their goal line.

Scotland were eventually ground down by the stronger South African pack, but how South African centre, Jesse Kriel escaped a TMO review, much less a red card is beyond me. His "tackle" was a direct head on head clash on Jack Dempsey that looked as bad as Tom Curry's red card offence against Argentina. Scotland will have other regrets in a game that was there for the taking, had they taken their earlier chances. They will provide a formidable challenge for Ireland in due course.

Looking forward, I have suggested that Andy Farrell might pick a radically revamped side to play Tonga next weekend, in a post that was not well received on the Irish Rugby Fan Forum. I doubt he will be so radical, but I think it is an argument worth making.

23 out of Ireland's 33 man squad saw game time against Romania and 7 played the full 80 minutes. Some, like Tadgh Beirne, looked utterly exhausted by the end, having played  80 minutes in 33 degree heat. If Ireland are to win the World Cup, they are going to have to share the load and trust their back-up players to be able to do a job when required. It would be unfair to expect them to be able to do so if they haven't had at least some game time in recent weeks, so the name of the game is squad rotation.

I would therefore try to avoid any players having to play two full 80 minutes in a row, and ensure all players have experience in playing in positions where they may be needed later. Assuming Sheehan is still injured, but all others have recovered, my team to play Tonga would therefore look something like this:

1.    Kilcoyne, sub Loughman
2.    Kelleher, sub Herring
3.    Bealham, sub O'Toole
4.    McCarthy, sub Ryan
5.    Henderson
6.    Baird
7.    Van Der flier
8.    Conan, sub Doris
9.    Murray, sub Casey
10.    Byrne, sub Sexton
11.    O'Brien
12.    McCloskey, sub Ringrose
13.    Henshaw
14.    Hanson
15.    Crowley

That would mean 14 changes from the starting line-up against Romania, with only McCarthy getting a second start. As he is being mentioned as a possible sub for the game against South Africa, in a 6:2 bench split to match that of South Africa, he needs all the experience against physical opposition players he can get.

The real bolter in the above selection is Crowley at 15. He is probably the only option we have for 23 is we go for a 6:2 bench split as the 23 would then have to cover for Sexton at 10 as well as the outside backs. He has met all high expectations so far, but can he play a full blooded test match at 15 or 12 in the event of injury? We need to find out.

The above is close to the weakest team we could field in the World Cup, with only Van Der Flier, Hansen, and possibly Henshaw guaranteed starters against the Springboks. It could lead to accusations of arrogance or complacency against Tonga, who are a good team with several ex All Blacks and Adam Coleman, an ex-Aussie in their ranks.

But which of the above players would let us down? All would have places in the team going forward to play for. None would be holding back, for fear of injury, as very few will see much game time going forward if they play poorly. Rugby is still often a game won by the team that needs it most, and most of the team that played Romania and who will be playing again against South Africa don't need another match in between.

Ireland have done badly at previous world cups because we have relied on the  same core starting XV who were either injured or knackered by the time we got to the quarter final. We need this team to be at their absolute peak for the matches against South Africa, Scotland, and, hopefully, New Zealand followed by Australia and France in the Semi-final and final.

Can we really expect most of them to be both injury free and at their peak for those 5 tough matches if they have to play against Tonga as well? World Cups are won by countries with deep squads and key players in prime condition to peak at the right time. If we can't trust a team made up of mostly back-up players to beat Tonga, do we really rate as contenders for this World Cup?

Besides, with Herring, Ryan, Doris, Sexton, and Ringrose on the bench, we are well placed to close the match out if it is still in the balance in the second half. Of course, it's a risk, resting so many front line players, but its all about  the risk reward ratio. The risk is relatively small, and the rewards of having a 33 man squad, all happy, motivated, and with serious game time under their belts going into the crunch matches of the competition could be much greater still.

We will undoubtedly need some of those back-up players to step up into the first XV later in the competition. What message does it send them if we don't trust them to do a job against Tonga? As South Africa are demonstrating, rugby is now a 23 man game. With injuries and fatigue, there is no room for passengers in the squad. The time to find out if some can't make the step up to top class rugby is now, with some proven match winners in reserve on the bench.

I will be watching the performances of Crowley and McCarthy, if selected, with interest. Both are relative newcomers displacing more experienced players like Carbery, Treadwell and Kleyn in the squad. Both could have a key role in determining whether we can beat South Africa and the big teams beyond. We depend on them to perform every bit as much as the established stars of the side - Sexton, Ryan, and Beirne. This is where we start to find out whether Ireland have the depth to be serious contenders for the World Cup.

Tonga beware!