The club is set to continue its rebuild through the NAB AFL Draft this November, placing pressure on fringe players hoping to earn new contracts and a number of rookies jockeying for senior list spots.
Harvey said the fact that Fremantle players were fighting for their careers would be a danger for Essendon on Sunday, but he said he wouldn't tolerate selfish football.
"This time of year you want to be playing well," Harvey said from Subiaco Oval on Thursday afternoon.
"I think that's the danger for any club that thinks they look like playing finals – you're always playing teams [with] players that are playing for contracts.
"That (selfishness) won’t be tolerated. You play your role."
Harvey conceded Fremantle's credibility took a hit in round 20, with the side losing to last-placed Melbourne by 63 points.
The coach said the most frustrating thing about the loss was the sudden and dramatic drop in form, and his players were sent into the boxing ring as a result on Monday morning.
"That happens quite often ... there's always different ways to train the mentality of your players," Harvey said, referring to the Monday-morning bouts.
"We'd been travelling well for three weeks we thought, and then put in a performance like that, so everyone's been put on notice.
"There's many facets to why they didn’t play well. I wouldn't call them teething problems, but a few guys are still getting used to playing on the road, and some guys' performances on the road [need to lift]."
Fremantle will be boosted by the returns of small forward Hayden Ballantyne and Roger Hayden, who hasn't played since he broke his leg in round nine.
Hayden returned through South Fremantle last week, splitting his time both back and forward, and Harvey said it would be up to Essendon to work out where he will be used on Sunday.
"It would be fair to say that he got through the game," Harvey said. "He's an important player for us and when Roger plays we have a good winning strike rate.
"I think what we've been able to do with the side and through unavailability, we've been able to try players in different positions and Roger's one of those."
Luke McPharlin will play his 150th match on Sunday and Harvey said the versatile key position player had room to improve.
"It would be fair to say ... the missing ingredient for Luke is that he needs to be playing in a successful team more regularly," the coach said.
"You probably wouldn't have thought he'd be playing forward during his 150th. There are different reasons that you do that as a coach with Luke [to] find out what he's got up the ground in more creative positions."
