Pittard missed last weekend's miracle win over West Coast with "general soreness" but was expected to recover in time to face North Melbourne in Hobart on Saturday.
Even when scans reveled the soreness was a slight strain of the hip flexor, the club still hoped he would line up.
But on Tuesday morning, coach Ken Hinkley ruled the running defender out, continuing Pittard's frustrations with injury.
The 22-year-old has only managed 18 games since being drafted with pick no. 16 at the 2009 draft and could only manage one game last season.
Hinkley said given his run of injuries in the past, the talented defender would be given time to recover properly from his latest setback.
"He's probably going to miss again and we've just got to be mindful that we know his history and I'm not going to rush him back to put him in jeopardy to miss a long period of time," Hinkley said.
"If he has to miss another week then so be it, if it extends out further than that then that'll be the case.
"At the moment we're hopeful that he'll probably be right the next week."
Pittard's absence adds further strain to a defence already stretched with the loss of key back Trengove, who underwent surgery on his fractured foot on Monday afternoon.
Initial estimates suggested Trengove would miss up to six weeks but Hinkley said the prognosis was now eight to 10 weeks.
He the club would know by Wednesday morning whether Trengove would be put on the long-term injury list.
"It's a significant blow obviously, he's a key back and he's one of our leaders more importantly," he said.
"We have to work with the personnel that we've got and make sure we can just move them around and get what we need."
The defensive losses come at a bad time for the Power, who face a North Melbourne unit boasting several in-form key forwards.
Small forward Lindsay Thomas has been exceptional in 2013 with 21 goals, Drew Petrie has booted 10 and Lachlan Hansen is also a chance to return to the line up this week.
Hinkley said his players would have to help each other out to negate the influence of the Kangaroos' talls and pick up the slack left by Pittard and Trengove.
"(Alipate) Carlile and (Tom) Jonas, (Cameron) O'Shea and (Justin) Westhoff can go down there and help us out," he said.
"They've got some big blokes down there and we just need to make sure we help the defenders as well as we can."
Harry Thring is a reporter for AFL Media. Follow him on Twitter: @AFL_Harry.
