Scrum half puzzle for England

England's first training run at Carisbrook Stadium on Monday began with a question mark over who will be their fly half at Rugby World Cup 2011 - but it is the vacant No.9 shirt that could prove more crucial.

England's talisman since RWC 1999 has been Jonny Wilkinson, who has the most World Cup points (249) and is pushing former understudy Toby Flood for the right to wear No.10.

While England know that both Wilkinson and Flood can do a job when called on, manager Martin Johnson will not want the uncertainty at scrum half that led to a leap of faith at France 2007 - albeit one that paid off as England reached the final.

Back then, Harry Ellis had just made the position his own when a knee injury forced him out of the World Cup and subsequently ended his career.

Andy Gomarsall, who was on a temporary contract with Harlequins and had nearly quit the game a year earlier, stepped in to form a consistent combination with Wilkinson and Mike Catt at inside centre.

The fact that Gomarsall's competitors for the shirt, Shaun Perry and the retired Peter Richards, are nowhere to be seen these days shows how hard it has become to nail down a role that, when performed badly, can leave the best teams rudderless and toothless.

Three in contention

The contenders to face Argentina on Saturday are Ben Youngs, Richard Wigglesworth and the uncapped Joe Simpson.

Youngs is first choice, but is recovering from keyhole surgery on his knee and has only 12 caps.

He may initially act as a replacement for Wigglesworth, who has just eight caps and is seen more as a utility player than a long-term No.9.

Simpson is an exciting wildcard, but nothing more at this stage.

The position has also proved troublesome for Argentina since the retirement of dominant former captain Agustín Pichot.

Coach Santiago Phelan has experimented with different options since Pichot hung up his boots after the third-place play-off victory against France four years ago.

Nicolás Vergallo is the frontrunner for the scrum half spot, though Alfredo Lalanne and centre Nicolás Sanchez are the other options. With just nine caps between them, however, they may struggle to stamp any authority on the game.