The Western Force face an emotional but otherwise largely irrelevant end to their Super 14 season after some dubious refereeing effectively scuppered their finals aspirations in Cape Town.

Force coach John Mitchell rued an apparent blunder from South African match official Marius Jonker after his side's 25-24 loss to the lowly Stormers on Saturday.

Needing a bonus-point victory to stay in finals contention, the Force recovered from a 12-0 deficit to lead 17-15 in the second half.

But the match turned decisively in the Stormers' favour nine minutes from the end when young fullback Joe Pietersen scored his second try to set up a 25-17 lead for the home side.

In a decision which Mitchell labelled "atrocious", neither Jonker or his assistants picked up what appeared a clear obstruction by Stormers centre Dylan des Fountain on Force counterpart Ryan Cross in the lead-up to the try.

Ultimately, the Force picked up just one bonus point for the narrow loss, leaving them in eighth position, six points behind the fourth-placed Crusaders with only a home game against the Highlanders on Saturday night remaining.

A win in their final-round fixture at Subiaco Oval would give the Force their highest-ever points total for a season, but is unlikely to help the Perth franchise equal or surpass their previous highest finish of seventh.

However, Mitchell and captain and lock Nathan Sharpe stressed the team would have plenty to play for in what will be a farewell appearance for at least seven players, including five Wallabies.

Matt Giteau and Josh Valentine are heading to the Brumbies next season, Drew Mitchell is linking with the NSW Waratahs, while Scott Staniforth and Tai McIsaac will play out their careers in Japan.

"Finals is gone for us, but we will look to finish as high as we can in the competition and we will continue to be attack-focused and proactive in our football," Mitchell said.

"Bear in mind that we've got a lot of team-mates that will be departing at the end of the game, so I think playing for each other and together it will be a special night.

"So we certainly won't be lacking motivation this week."

A second try to Giteau inside the last five minutes, which contributed to the star five-eighth's 19-point personal haul, wasn't enough to save the Force's season.

"I thought we lacked intensity in our first half, but we changed that in the second and I'm very proud of the way the boys played in the second half," Mitchell said.

"I don't really question decisions, but that blatant blocking late in the game when they were awarded a try was just an atrocious decision.

"The players stopped. It was very clear on TV. You would have thought that the assistant referees would have made a decision."

The Force secured plenty of territory and possession, particularly in the first half, but several promising raids broke down due to poor execution.

Mitchell felt the dewy conditions contributed to the Force's high mistake rate as much as their anxiety over the need to score multiple tries.

Mitchell said there were injury doubts over prop Ben Castle (AC joint) and hooker McIsaac (calf) for the Force, who will have just one full training run this week after returning home on Tuesday.

There is also a question mark over No.8 Richard Brown (ankle) who re-signed with the Force for two more years on Saturday when Hurricanes prop Tim Fairbrother also agreed to join the Perth-based franchise.

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