So what might Manning have learned yesterday as his team flopped to its sixth straight defeat and he was pulled in the fourth quarter with a zero quarterback rating?
That his team is sinking like the Times Square ball on New Year's Eve? That it hurts to get hit really hard?
After New York's 37-14 loss to the Ravens, Coughlin suggested there is still learning to be done in ugly defeat - even if that learning is primarily about coping with failure.
"This is something Eli is going to have to learn to fight his way through," the coach said. He conceded that Manning got "tied up" mentally against an aggressive Ravens defense, but that he hoped his quarterback, who turns 24 on Jan. 3, will return with "a hunger."
"I'm sure he's disappointed," Coughlin said. "I don't think it's a confidence thing."
Even though he was replaced by Kurt Warner yesterday, Manning will remain the No. 1 quarterback on Saturday when the Giants host the Pittsburgh Steelers, Coughlin said.
Whatever lessons were imparted on this year's No. 1 draft pick, they came with a price.
Manning, who lost his fourth straight since starting his first game against the Atlanta Falcons on Nov. 21, was blitzed and battered by the Ravens, completing four of 18 passes for 27 yards and two interceptions.
His timing was off even after the game had ended. Wearing a pinstriped suit, he stepped into the media room early - while Warner was still at the podium - and stared at the ground for an awkward few minutes waiting for his teammate to finish.
Manning seemed to agree with Coughlin that pain is part of the maturation process. He disagreed with the premise of a question that perhaps he'd be better off learning from the sideline.
"Even if you're learning the hard way, you're still learning out there," he said. "Coach Coughlin, he's sticking with me. He understands it's rough now for a rookie quarterback."
Among his biggest concerns, Manning said, is keeping the faith of his teammates. "I don't know if I've lost it or not," he said.
Warner entered with six minutes left and led a six-play, 78-yard drive ending with Tiki Barber's 1-yard run. It was New York's first offensive touchdown since Jeremy Shockey scored against the Falcons.
Warner said "it felt great" to play for the first time since a Week 10 loss to Arizona.
Warner said Manning fell victim to a defense that "did a lot of confusing things" such as employing varying blitz packages. But the seventh-year veteran said he agreed Manning should still start because "this guy is the quarterback of the future for the New York Giants. Period."
The Giants (5-8) finished with six turnovers. Particularly embarrassing was Manning's fumble in the third quarter without being touched. The Ravens' Kelly Gregg recovered on New York's 14, and the Ravens scored their final touchdown four plays later.
NOTES: Giants linebacker Barrett Green left the game with a sprained knee in the first quarter and did not return. ... Barber, praised this season for cutting down on his fumbles, lost two yesterday.