Some union members, apparently angered at potential changes to pension plans for new city employees and the impending threat of massive layoffs, booed Nutter when he took the stage.
"You put all that together and it's not a surprise to me that there will be a few people upset," Nutter said after the event.
Nutter is stuck between municipal unions and the state General Assembly at the start of what he calls "the most important week in the city in the last 50 years."
The General Assembly holds the power to approve two proposals that would raise $700 million to balance the city's five-year financial plan. Nutter and City Council are asking legislators for the right to increase the 7-cent sales tax by 1 cent on the dollar for five years and defer payments to the municipal pension plan.
The House, controlled by Democrats, passed legislation for those measures on Aug. 5. The Senate, controlled by Republicans, approved the legislation on Aug. 26 after amending it with sweeping language that impacts the pensions of thousands of municipal workers across the state.
Democratic House leaders, lobbied by union leaders opposed to the Senate amendments, vow to make their own alterations to the legislation in advance of a new vote, planned for Thursday.
That puts the city, as Nutter puts it, "in a place we don't want to be" - with the legislation bouncing back and forth from the Senate to the House.
The Pennsylvania Intergovernmental Cooperation Authority, which oversees the city budget, will meet Friday to vote on a fallback budget drawn up in case the General Assembly fails to reach an agreement on the legislation.
That budget calls for layoffs for 3,000 city workers, including hundreds of police officers and firefighters, along with service cuts and the closures of every library branch and recreation center.
Those layoff notices would be issued Sept. 18. Employees would start losing their jobs on Oct. 2.
Nutter said that he remains in "constant communication" with legislative leaders from both parties about the city's budget crisis. He has found them in agreement on one issue - they don't want the fallback budget put into action.
"This is a very serious moment in the history of the city," Nutter said. "The things that we've talked about, which I don't want to do, don't have to happen."