He challenged his seniors, telling them: "You're either going to have six opportunities (remaining) or seven — you choose."
Fitzgerald then benched four of his defensive starters.
But the shuffling did little good, as the Wildcats allowed an anemic Penn State offense to romp in a 34-24 victory before a disappointed homecoming crowd of 40,004 at Ryan Field.
Northwestern (2-5, 0-4 Big Ten), which did not force a punt until midway through the third quarter, lost its fifth straight game and now is a long shot even for the Motor City Bowl.
The Wildcats led 21-20 and were driving just before halftime. But before a third-and-3 from the 8, they called a timeout with 56 seconds left rather than letting the clock get closer to 30.
They settled for a field goal and gave Penn State (7-1, 4-0) just enough time to seize momentum — and a 26-24 lead — by going 63 yards for a touchdown.
"I thought if we took (the clock) down and then got a first down, we'd be hurting for time," Fitzgerald explained. "That was probably a bad choice on my part."
Northwestern was driving to start the third quarter until Dan Persa had a pass tipped that linebacker Gerald Hodges grabbed and ran back 63 yards to NU's 19. Tailback Silas Redd took it to the house on the next play.
Matt McGloin entered completing 57.1 percent of his passes but had a field day against NU's new-look defense, completing 17 of 26 attempts for 192 yards.
Fitzgerald, clearly sick of watching a defense that ranks among the nation's worst against the pass, inserted five new starters, one the result of injury. Kevin Watt played for end Tyler Scott, who suffered a neck stinger in practice Tuesday.
Safety David Arnold replaced Ibraheim Campbell. End Vince Browne was benched in favor of Quentin Williams. And linebackers Damien Proby and Chi Chi Ariguzo replaced David Nwabuisi and Bryce McNaul, who had been limited in practice by an undisclosed injury.
"It's not necessarily demoting guys," Fitzgerald said. "It's trying to put guys in roles that can spark them."
While NU's defense clicked in the second half, allowing just 88 more yards, the offense went dormant. The line gave up five sacks, and Jeremy Ebert dropped a potential touchdown pass.
"My fault," Ebert said.
Persa left the game with just less than 10 minutes left with an apparent turf toe injury on his left (non-Achilles' repaired) foot. Fitzgerald said he could have returned to the game.
Replacement Kain Colter took sacks on the next two plays. They knocked his team, down 34-24, out of field goal range.
And all but out of hope.
"Everyone's extremely frustrated," safety Brian Peters said. "We have to turn that frustration into motivation and start making things happen for 60 minutes."