But the Blues flanker says the players were fully behind sacked coach Gareth Jenkins and his management team and denied that player power meant there was doubt over the game plan.
He also believes he is leaving the game in Wales in good hands, with plenty of talent coming through – and he thinks the players he is leaving behind can bounce back by winning the Six Nations title this season.
WRU Audio: Listen to the full interview with Martyn Williams
“Apart from the last 80 minutes the World Cup was enjoyable. We had a good summer together and gave it our all,” said Williams, in a special interview for the WRU website.
“It is just a total shock that we are not still involved, this is the quarter-final weekend and we are sitting at home twiddling our thumbs when we should be preparing.
“I am sure that nine times out of 10 we would beat Fiji, it was just that one game they played to the max of their potential and we did not – we only have ourselves to blame for that because we got into a position to win it and then let them back in.
“All in all you cannot paper over the cracks of going out at the group stages. When I scored the try near the end my initial reaction was that if we could win the kick off it would be fine and then we could kill off the game.
“We let them back in, they regathered, we did not see the ball for four or five minutes and they ended up getting the try. It was basic error again which cost us and means we are back home which is not where we want to be.
“It is very frustrating and disappointing when you hear comments about the not playing for Gareth Jenkins. If you look at the whole World Cup, no-one can doubt our effort or our endeavour, we gave absolutely everything to the cause, if anything it was just the top three inches which let us down tactically.
“Those comments come from people who were not in the squad, but when you have been around for 11 years you realise that is what happens in Wales. People look for reasons that were not there, the basic fact was that on the day Fiji played that little bit better than us.
“Player power has been blown out of all proportion again. Every team has a senior player group who will have strong opinions and that is what the coaches and senior players are there for.
“You are never going to agree fully but at the end of the day the coach is the number one guy and what he says goes, and the boys will listen to that. People are looking deeper than what is actually going on.
“It was frustrating as a player because we felt that over the last 18 months we had given absolutely everything, worked as hard as we can – both the management and the team together – and the frustration of not getting through means people are looking for things that are not there.
“I am still relatively young but I have been playing 11 years and the body and mind can only take so much. With a young family as well, international rugby is a huge commitment and it is a privilege to do it as long as I have but now is the right time.
“It goes in four year cycles and as soon as this one is over you are preparing for the next one. I certainly won’t be around for the next World Cup so it is time now to step aside for someone younger to come through.
“I did not make the decision after the Fiji game, it was probably during the last Six Nations that my next goal would be the Rugby World Cup and get selected in that squad – things did not go as I would have planned and liked in the tournament but the decision was made and I think it was the right one.”