Gone to ground ... Sitaleki Timani, a member of the "other" Tongan squad playing at the SFS tonight -- those Waratahs players with a Tongan connection -- checks out team training from the stadium's turf.

Gone to ground ... Lopeti Timani, a member of the "other" Tongan squad playing at the SFS tonight -- those Waratahs players with a Tongan connection -- checks out team training from the stadium's turf. Photo: Steve Christo

WARATAHS coach Michael Foley is hoping an unpredictable Tongan side gives his injury-depleted squad plenty to think about in its final trial at the SFS tonight.

The withdrawal of Wallabies hooker Tatafu Polota-Nau was the latest injury to hit the Waratahs a week out from their Super Rugby season-opener against traditional rivals the Reds.

Polota-Nau will join fellow Test representatives Rocky Elsom, Dan Vickerman, Lachie Turner and Drew Mitchell on the sideline tonight but is expected to be available next weekend.

And while a largely inexperienced Tonga - who will feature none of their World Cup players - are not expected to pose the Waratahs too great a threat, the trial will provide vital game time for wingers Brackin Karauria-Henry and Tom Kingston, as well as replacement hooker Damien Fitzpatrick.

Fitzpatrick was told on Wednesday he would be elevated to the side for the first two quarters. John Ulugia will come off the bench to play the third and fourth quarters.

''I'm very pleased,'' the 22-year-old said after the Waratahs' captain's run yesterday.

''It's not good that Taf went down, and you don't wish that on anyone, but with injury comes opportunity, so I'm looking to take that definitely.''

Foley was also talking about ''opportunity'' yesterday. ''Damien played particularly well last week. He's a guy that's going to play more game time this year and we've got John Ulugia who's the third hooker,'' he said.

''We played him at tight-head last week, so he's a prop for us, but he's also a hooker so he'll get an opportunity to play [tonight]. So it's good for Taf that he's having the rest and I'm pretty excited for Fitzy as well.''

Foley said NSW had not analysed their opponents, who will back-up to play the Junior Waratahs on Sunday as part of the Pacific Rugby Cup. He said the unknown element would be good for his squad.

''I think what we wanted to achieve with the Samoan game is not dissimilar … whatever they throw at us, we need to be able to cope with and we need to be able to make adjustments on the run,'' he said. ''We obviously have some plans to implement in the game but, last week, we had torrential rain which no one expected, and I thought the guys adjusted particularly well. I hope it's particularly unpredictable from them, and we see how we cope in different circumstances.''

Foley also downplayed the impact of Wallabies second-rower Vickerman's possible retirement.

''I think Dean Mumm, Kane Douglas, Sitaleki Timani and Greg Peterson present you with some pretty good options, and Richard Stanford, who's got Super Rugby experience, has been training with us,'' he said.

''He played in our trial last week and he'll play again tomorrow night, and Dave Dennis, who's playing very well at six, can also play lock.''