White was subbed out of the club's three-point win over Melbourne with groin tightness and hasn't recovered.
Coach Ken Hinkley compared White’s injury to that of Power defender Tom Jonas, who missed four weeks earlier in the season battling osteitis pubis.
Hinkley was unsure when White would again be available for selection.
"White's going to miss, he's not going to play, he's struggling with a bit of a groin," Hinkley said on Thursday morning.
"It could be a couple (of weeks)...we've had the bye so we're going to give him another week and then hopefully he'll be ok.
"We did a similar thing with Tom Jonas...he ended up missing three or four games but we've now got him back in great shape. So we're mindful of that, we don't want to run Whitey into the ground."
Hinkley said the loss of White magnified the importance of Monfries' return.
Although goalless in his previous three games before a hamstring injury, the 27-year-old was still able to contribute defensively for the Power and limited Adelaide’s Brodie Smith to a season-low nine possessions in round 15.
Now that Monfries has recovered, Hinkley expected increased offensive output.
"Monfries' game against Smith was a really good game for us as far as limiting the damage a bloke like that can do," he said.
"But we need him in the side to help us create some stuff too."
Sunday's clash against the wounded Magpies could prove crucial to the Power's hopes of securing a top-four finish, with victory required to stay in touch with those at the top of the table.
Collingwood fell out of the eight last weekend, suffering its third consecutive loss and its fourth in five games.
Like a cornered beast, Hinkley predicted the poor results for Nathan Buckley's men would only make them more dangerous.
"Every side in this competition is very dangerous when you put a bit of pressure on," he said.
"I'm sure 'Bucks' is not talking about the pressure from outside, he's talking about the internal pressure and we're the same here; we're talking about the internal pressure that we need to perform the way have to."
