Speaking at the club's annual general meeting, Petrie urged supporters to return to Easter Road to avert the potential for a second successive annual financial loss after recently reporting a second loss in eight years.
"Growing the attendances by Hibernian supporters is our core strategy," the Hibs chairman said.
"We are asking supporters to do what you do best - support the team at home matches. If we cannot do that, and if we cannot grow our income, then the only route to get back to break-even will be to make substantial reductions in costs.
"The club is asking shareholders, supporters and everyone connected with the club to play your part in getting back to where we all want it to be."
Much of the cost was attributed to reforming the team under former Bohemians manager Fenlon for the battle to avoid relegation, which was successful.
The same team reached the William Hill Scottish Cup final, losing 5-1 to Hearts, a result Hibs apologised for.
Petrie accepted responsibility for the appointment of Colin Calderwood, Fenlon's predecessor, as manager. The former Scotland defender is now assistant boss at Norwich after he was sacked by Hibs, only a few months after being linked with jobs in England.
Petrie added: "The way things worked out, the appointment of Colin Calderwood was not a good one. Mistakes were made. As chairman, I take responsibility for that. I am sorry that we have all had to endure two seasons of under-achievement and decline.
"I would also like to thank Pat Fenlon for accepting the post of manager at a particularly challenging time and for attacking the task of rebuilding the squad with conviction. Pat himself will tell you that it is still a work in progress as we approach the January transfer window."