The Western Force, who have already lost Rugby League convert Jordan Rapana for the entire season, will be without three of their key forwards when they face the Brumbies in a Super Rugby pre-season trial in Darwin on Saturday.

Force coach Richard Graham confirmed on Friday that the young recruit, Rapana, will miss the entire season, after he underwent shoulder surgery - following an injury he suffered at training last week. The former NRL speedster underwent a full shoulder reconstruction.

This blow follows the loss of New Zealand import Willie Ripia, who was forced to quit after being caught stealing from his teammates.

Rapana, who played with the Gold Coast Titans in the NRL before embarking on a two-year Mormon mission, is contracted to the Force until the end of 2013.

The Force coach, Graham, also revealed that captain David Pocock and veteran Nathan Sharpe will not be part of the playing roster in Darwin.

Pocock has been rested after enduring a hectic 2011 campaign, while Sharpe is nursing a minor calf complaint.

Fellow Wallaby Richard Brown has also been ruled out as he recovers from a serious shoulder injury.

"It's all about managing the squad and ensuring that come February 24 - when we take on the Brumbies in Canberra to open the season - we've got a fit and healthy group to choose from," Graham said.

"Getting game time into the squad is important and as such we've prepared well and will be using the match in Darwin to put some structures together.

"We haven't taken any unnecessary risks with players who are finalising their recovery programmes or who might have a niggle that needs a little more time to get right.

"For guys like David Pocock and Nathan Sharpe, they played a lot of rugby at the back end of last year and I felt the best thing was to get additional conditioning into them without the physicality of a game," Graham said.

Despite the absence of Pocock, Sharpe and Brown, the Western Force believe their forward pack still takes on a menacing look.

Salesi Ma'afu, Pek Cowan, Matt Hodgson and Ben McCalman are all Wallabies, while 2011 standouts Kieran Longbottom and Sam Wykes are also in the mix.

Wykes has been appointed captain, and after leading the team during a post-season tour against the Samoan World Cup squad last year is keen to further his leadership credentials as well as consolidate his performances after a breakout year in 2011.

"We have a great bunch of guys who have gelled really well.  Over the past three months of pre-season training everyone has worked hard and is now looking forward to putting that into practice on the field," Wykes said.

"Every time you put on the jersey you want to win but at the same time the result isn't the most crucial aspect of the trial period.  We're all really keen to play and dust off the cobwebs, get some match fitness and build towards the season."

Graham selected a 27 man squad to compete in Darwin.  The side features a number of the franchise's key recruits including Ma'afu, who will play against his former side, while Fijian international Napolioni Nalaga will suit up for his first match in ocean blue.

The Western Force will take 14 forwards and 13 backs to Darwin and with no limits to the number of substitutes in the match Graham said it was important that there were enough bodies to spread the load across the group, especially with stifling weather conditions expected.

Amongst the 27 man squad are five local West Australian franchise players who'll bolster numbers after a host of contracted squad members are eased back into competition or given additional time to complete recovery programmes ahead of the season proper.

Nalaga will be one to watch in the backs having shown his try scoring prowess in several stunning seasons with French side Clermont.  Of the other new recruits to the Western Force, Winston Stanley will play as will young flyhalf Ben Seymour and wing Samu Wara.

Exciting young West Australian scrumhalf Justin Turner will make his return to competitive rugby on the weekend after coming back from consecutive knee operations that have kept him out since late 2010.

Two of the five WA franchise players being given their opportunity, Palmyra lock Jake Ball and Cottesloe flank Ryan Hodson, have been training in the Western Force professional programme since pre-season started last November on the invitation of Graham.  The others include Level 1 Academy member JP Pretorius, who won the most improved player award for his efforts with Nedlands in the 2011 Premier Grade season, as well as Neddies wing Cam Crowley and Wests Subiaco fullback Chance Bunce.

With a forecast in Darwin on Saturday of 33°C, storms and high humidity, kick-off will be 19.00 to beat the heat of the day and the match will be played in four 20 minute quarters to allow players to rehydrate on a more regular basis.

"Trial games are about challenging your players and getting them back into competitive game conditions however their welfare is our top priority and all the necessary precautions have been taken," Graham said.

"We've had a good build-up during pre-season and have put in a lot of work.  This is the next step in our preparations and it will be positive for the players to feel that body on body contact in an unstructured environment," Graham said.

Western Force:

Forwards: Jake Ball, Phoenix Battye, Nathan Charles, Angus Cottrell, Pek Cowan, Tetera Faulkner, Matthew Hodgson, Ryan Hodson, Kieran Longbottom, Toby Lynn, Salesi Ma'afu, Ben McCalman, Ben Whittaker, Sam Wykes (captain).

Backs: Chance Bunce, Cam Crowley, Nick Cummins, Alfie Mafi, Napolioni Nalaga, JP Pretorius, Ben Seymour, Brett Sheehan, Rory Sidey, Winston Stanley, James Stannard, Justin Turner, Samu Wara.

Date: Saturday, February 4
Venue: Rugby Park, Marrara (Darwin)
Kick-off: 19.00 (09.30 GMT)
Referee: Ian Smith
Assistant referees: Simon Moore, Jake Barlow