Defense Secretary Robert Gates made it clear this week he doesn't want the general saying that - or giving any other opinions - in public anymore.
But just a few weeks ago, McChrystal talked freely with CBS News correspondent David Martin in Afghanistan about what he believes it will take to win. His report tonight draws on never-before-seen portions of that interview.
After eight years of fighting the clock is running out for the U.S. in Afghanistan.
"I believe it's our most important chance now," McChrystal said in the interview. "You can never say there wouldn't be another, but I wouldn't count on one."
Everybody knows McChrystal wants more troops, but when he spoke with "60 Minutes" in August he made clear more troops alone will not defeat the Taliban.
"We're going to change the way we operate," he said, by "connecting with the people in a way that the people don't believe that you're an outsider and occupier."
McChrystal wants to see less traditional warfare - airstrikes, ambushes, raids - and more cooperation - soldiers helping to protect civilians.
But he knows American troops - whether they're protectors or occupiers - can't win this war by themselves. He needs to vastly increase the size of Afghan forces.
"I'm recommending about a total of 400,000 people between the army and the police," he said - doubling its current size.
McChrystal admitted, "It'll take us longer than I'd like."
But McChrystal believes he only has 12 months to turn this war around, and that's not time enough for the Afghan government of Hamid Karzai to put its house in order.
"There's corruption in the afghan government at senior levels," he said.
When Marines launched an offensive into Helmand province in southern Afghanistan, the stated goal was to cut off the Taliban from their primary source of money - the annual poppy crop. But McChrystal's deputy, Lt. Gen. David Rodriguez, told CBS News there was a second objective.
"It's not only the money for the, for the Taliban," Rodriguez said. "It's also some corruption that's in the Afghan leadership, in part of their government, their security forces too for that matter."
The operation in Helmand is denying both the Taliban drug money and government officials drug money.
"It's a balance of both," Rodriguez said.
Rodriguez himself represents a change in the way the U.S. is fighting this war. incredibly enough. This is the first time a single commander has been in charge of day-to-day operations throughout the entire country.
What American forces need most in Afghanistan, says Maj. Gen. Mike Flynn, McChrystal's top intelligence officer, is a few quick wins - by which he means not military victories but convincing Afghans they will be better off siding with the U.S. than with the Taliban.
"What we've got to do in 12 to 18 months is just show that we basically know what we're doing out here," Flynn said. "There's some glimmers of success that we need to show."
Eight years of fighting and the U.S. is still looking for glimmers of success.