WARATAHS officials last night argued they had not wasted money on an "injury-prone" player following the announcement their star signing Timana Tahu could be sidelined until May because of hamstring problems.

Waratahs coach Ewen McKenzie and NSW Rugby Union chairman Arvid Petersen said if they sorted out Tahu's injury now, NSW and the Wallabies would get value out of their four-year investment.

And the decision to correct the 27-year-old's running style in a bid to eradicate his lingering hamstring troubles has been endorsed by Wallabies coach Robbie Deans.

"NSW have bitten the bullet and gone to get him 100 per cent right. If you take short cuts, sooner or later, they bite you," Deans said yesterday.

However, McKenzie conceded some people would describe Tahu as "a crock".

McKenzie said the Waratahs and the Australian Rugby Union had investigated Tahu's medical history before deciding last season to lure him from league and sign him to a four-year contract.

"We were pretty thorough in the work we did in checking Timana's medical history before he came across. There was a little bit of history, but it wasn't all about hamstring injuries," McKenzie said.

"Even what he has got now is not a major issue, but it's enough to impede him mentally about playing 100 per cent. When he gets the ball we want him running 100 per cent.

"If we now try and work on his running style and the muscles he is using, we'll get more out of him. It's achievable.

"It's a four-year investment for us and the ARU. We could drag it out and keep Band-Aiding it. But we might as well be honest about it. For us and him, getting it sorted out right now is the best process."

As big a surprise as Tahu's lengthy absence was his admission this week that he had held himself back from running at full speed for nearly seven years because of fears about his hamstrings.

This prompted Waratahs captain Phil Waugh to remark: "I was surprised when I read the quotes in the paper this morning.

"He's dominated rugby league when he's appeared fit. And for him to come out and say he's only been about 90 per cent … well, I can't wait to get him at 100 per cent."

McKenzie added that Tahu's problems since moving to union emphasised the difference between the rugby codes.

"I'm not trying to denigrate

league, but the way the positions are played are different," McKenzie said. "And what we are wanting him to do requires different body mechanics. It hasn't got anything to do with Parramatta or the Newcastle Knights league teams.

"It's what we are asking him to do needs slightly different body mechanics. We just need to tweak it a bit.

"Everyone just assumes with outside backs there's a natural transition. But the physiological requirements of the two codes are different.

"And the new experimental laws highlight it even more. It's a speed game, and guys who can't match the pace are getting caught out."

And although Tahu is one of the Waratahs' main crowd attractions, the NSWRU board has no qualms about his being rested.

"We support Ewen's view on this," Petersen said. "He is quite adamant that in the short term it is important to get this corrected.

"Apparently, it is very correctable and can be improved on. Hopefully we can get it fixed in the next five, six, seven weeks, and Timana will be back in full flight."

The Waratahs travel to Christchurch today after making one change to the starting line-up to play the Crusaders tomorrow night because of rotation.

Dean Mumm takes Will Caldwell's second-row spot, while Wallaby halfback Josh Valentine moves to the bench. If Valentine takes the field it will be his 50th Super rugby appearance, which includes 38 games with Queensland.

WARATAHS: Lachie Turner, Alfi Mafi, Ben Jacobs, Tom Carter, Lote Tuqiri, Kurtley Beale, Brett Sheehan, Wycliff Palu, Phil Waugh (c), Rocky Elsom, Dan Vickerman, Dean Mumm, Matt Dunning, Adam Freier, Sekope Kepu. Res: Tatafu Polota-Nau, Al Baxter, Will Caldwell, Beau Robinson, Josh Valentine, Sam Harris, Rob Horne, Benn Robinson.

CRUSADERS: Scott Hamilton, Kade Poki, Casey Laulala, Tim Bateman, Caleb Ralph, Daniel Carter, Andrew Ellis, Mose Tuiali'i, Richard McCaw (c), Kieran Read, Ali Williams, Brad Thorn, Greg Somerville, Corey Flynn, Ben Franks. Res: Ti'i Paulo, Wyatt Crockett, Michael Paterson, Nasi Manu, Kahn Fotuali'i, Hamish Gard, Sean Maitland.