Grover will miss the trip to AAMI Stadium with a calf strain that was revealed on Monday, while McPharlin hasn't recovered as hoped from a hip injury.
They join Des Headland (calf) and Michael Johnson (ankle) on a horror injury list, while Paul Hasleby (calf) and Stephen Hill (hip) will have to get through Wednesday's closed training session to be considered.
Rookie Clancee Pearce, 18, will be elevated to make his debut on Saturday night as coach Mark Harvey searches for injury cover.
"Three out of those four guys that are out are in our leadership group, which is significant," Harvey said from Fremantle Oval on Wednesday.
"I don't think I've been through a list like this as in the injuries so early in the season.
"It is [challenging]. But you find out a lot about your list and the resolve and what you can do when a lot of things aren't going right for you.
"We travel to Adelaide where it's possibly going to be raining on Saturday night, and have a young, enthusiastic side."
The coach said livewire forward Hayden Ballantyne, 21, was also in the selection mix after a superb five-goal return to football in the WAFL at the weekend.
"We just need to make sure that he is fully right," Harvey said.
"We're happy with his form last week and we obviously have to make a few changes on the back of last week.
"He had an exceptional game last week, but you don't want a guy limping into his first game.
"I think once we get him in you'll see him in for a substantial period of time."
The WAFL's Foundation Day fixturing has also provided Harvey with an unwanted headache, with potential inclusions Adam Campbell, Ryan Murphy, Zac Clarke and Daniel Gilmore playing on Monday.
Harvey said he would only consider one of the four players coming off a five-day break at selection this week.
"You're running too much of a risk playing three or four guys with a five-day break," he said.
"And these guys won't be experienced at AFL level as in total games, so you're sort of playing with fire a bit.
"The five-day break is a bit of a problem for us, with the guys who played on the Monday."
Clarke and Kepler Bradley, who has missed three weeks with a knee injury, are the options to cover back-up ruckman Johnson.
Harvey said with Pearce definitely playing and Ballantyne in contention, he had to balance how many first-gamers he called on against Port Adelaide.
"We're playing a seasoned team with their back against the wall after losing their last two," Harvey said.
"Obviously they're right at the forefront of being a top four side. They've got a lot of experience in their side and they've got some really good ball users."
