The Wales head coach, Warren Gatland, who has twice changed a winning side in this year's Six Nations, is keeping his players guessing before next week's Triple Crown encounter against Ireland at Croke Park.

Even Shane Williams, whose two-try returns against both Scotland and Italy have taken him to within one of Gareth Thomas's national record of 40, says he is not sure of a place in the starting line-up in Dublin as Wales look to take their fourth step to a second Grand Slam in three years.

"The coaches are using training as a means of selection," said Williams. "Their view is that, if you do not train well, you are not going to play well. It makes sure the attitude of everyone is right and no one can take his place in the side for granted.

"Three victories have given everyone self-belief and, while I have been pleased with my contribution so far, I have to be picked for the Ireland game before I can talk about it. You never know what's going to happen with this management team and that's the way it should be."

Williams could end this season's Six Nations Championship as a Grand Slam winner and Wales' record try-scorer.

A single try at Croke Park would haul 31-year-old Williams level with Thomas, equalling a record it took Thomas 100 caps to compile.

Williams could also get there in a remarkable 45 fewer games, when a 40th try would also see him match the combined tallies of Wales greats Gareth Edwards and Gerald Davies.

Williams said: "I seem to be getting better the older I get - and I hope that can continue for a while. I am relishing going out on the field and loving every minute of it. That's the most important thing, enjoying your sport.

"The day I go out on the field dreading playing or not wanting to play is the day I will hang (up) my boots, but at the moment I am as hungry as ever. I am a striker - I enjoy scoring the tries. That's my job, but I don't really set myself targets.

"The last couple of seasons, I've scored a number of tries due to the fact I am getting involved in games a lot more. I am a lot happier when I've got my hands on the ball."

Williams' blistering form this season has seen him move him into 10th above French hero Serge Blanco on world rugby's all-time list.

Thomas and Australian full-back Chris Latham are each one score above Williams - while even the likes of All Blacks trio Joe Rokocoko (43), Jeff Wilson (44) and Christian Cullen (46) are within touching distance.

Williams added: "Everyone keeps asking me about these tries, but I am trying to avoid it as much as I can. To begin with, I have got to be picked for the Ireland game - so let's not get ahead of ourselves.

"I said before the World Cup last autumn that I felt very sharp. My fitness is probably better than it has ever been, and I am stronger and quicker than ever as well - so I feel very good. It would mean everything to break the record.

"Alfie (Thomas) is up there at the moment - he is a great friend of mine and one of the best - and to be able to say I have beaten the likes of people like Gareth Thomas, Ieuan Evans, Gerald Davies and Gareth Edwards is incredible."

Nine of England's victorious squad in Paris will clash head-on on Tyneside tonight after Wasps and Newcastle declined to give any of Brian Ashton's battered Six Nations troops a mid-tournament respite.

With the exception of James Haskell, who has an ankle injury, Wasps have named their strongest available side for a game the European champions need to win to enhance their prospects of finishing in the top four of the Guinness Premiership. It includes Danny Cipriani at outhalf with Josh Lewsey at fullback opposite another England contender Mathew Tait.

Cipriani, Lewsey and Tait - who has signed a new one-year contract with the Falcons - have all been touted as possible starters in place of Iain Balshaw at number 15 against Scotland tomorrow week.

The only one dismayed by the focus on individual match-ups is John Fletcher, Newcastle's director of rugby, who thinks the debate about specialist backline positions is a waste of time. "They should take the numbers off the back of the shirts, or have squad numbers, because all this stuff about pigeon-holing players as inside centre, outside centre or fullback is just nonsense," said Fletcher.

"The way the game is played these days, you will hardly ever see players line up in what you would call an orthodox pattern. Matt Tait is no different and, when people ask me his best position, I just say he's an outside back."

All Black wing Rico Gear has been forced to pull out of tonight's other Premiership game between Worcester and Sale in Stockport. Gear has a hamstring problem and will be replaced in the Warriors' starting line-up by Marcel Garvey. Guardian Service