Pietsch is yet to play this Super Rugby Pacific season and the 27-year-old has already been ruled out of the upcoming three-game road trip against Moana Pasifika, Highlanders and Hurricanes.
If all goes well, Pietsch will return following the Force's bye in the March 28 home clash with the Chiefs.
"He's aggravated the plantar fascia tendon in his foot," Force coach Simon Cron said ahead of Friday's clash with Moana in Pukekohe, NZ.
"And he's a power athlete. We're kind of waiting, get him to the bye, and see how he goes through that bye week with his prep.
"Ideally he's back by that stage, but it's a case by case basis."
It's been a frustrating period for Pietsch, who broke his jaw during the Wallabies' win over South Africa last August.Â
The Force are winless and bottom of the table after following up their 56-24 loss to the Brumbies with a 42-32 defeat to the Blues.
In better news, Wallabies enforcer Nick Champion de Crespigny (knee) could return either next week or the week after, while one-capped Wallabies winger Darby Lancaster will make his Force debut on Friday after recovering from a thigh injury.
Lancaster scored five tries from seven appearances with the Waratahs last season and Cron feels like the best is yet to come for the 22-year-old former Sevens star.
"From the moment he came over to us and started training and working with the team, he's been so exciting," Cron said.
"I'm ecstatic to get him back. He's got X-factor, he's got speed. He's a student of the game.
"We haven't seen the best of him yet. We're hoping we can be a part of his pathway back into the Wallabies.
"He's got all the talent and skill and drive to go a very long way, for a long period of time."
Hooker Nic Dolly returns to the Force starting side, having recovered from the knee injury he suffered on the morning of the club's tour game against the British and Irish Lions last June.
Moana started their season with a 40-26 win over Fijian Drua before being brought back to earth last week in a 52-10 loss to the Hurricanes.
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