Sunday, he showed what he couldn't do.
He was incapable of pulling himself from a wild-card playoff game against Seattle — Redskins coaches couldn't, either — and the results were stomach-turning. Washington lost, 24-14, and Griffin suffered an injury to his already weakened right knee, which with 6 minutes 19 seconds left bent in an unnatural way as he chased a low shotgun snap.
After several minutes on his back, Griffin was able to hobble off the field unassisted. He made a beeline for the locker room, the packed house at FedEx Field somberly chanting his name.
"I think I did put myself at more risk by being out there," he said. "But every time you step out on the football field, you're putting your life, your career, every single ligament in your body in jeopardy. So that's just the approach I take being out there. My teammates needed me out there, so I was out there for them."
On the play in question, the Seahawks recovered the ball at Washington's five-yard line. They wound up kicking a 22-yard field goal for their 24th unanswered point after falling behind, 14-0, in the opening quarter.
Knocked back on their heels by consecutive Redskins touchdown drives, the Seahawks responded with a smothering defense and typically impressive play by rookie quarterback Russell Wilson, who burned the Redskins with his feet and his arm.
Wilson completed 15 of 26 passes for 187 yards and a touchdown, and added 67 yards in eight carries.
Seattle's Marshawn Lynch rushed for a game-high 132 yards in 20 carries, including a 27-yard touchdown run that gave Seattle its first lead, the only one it would require.
"It's a big comeback," said Seahawks Coach Pete Carroll, whose team ended Washington's seven-game winning streak. "The setting of this crowd, and as much momentum as they had, it's a marvelous statement. It ain't about how you start, but it's about how you finish, and we've been saying that forever."
Of the four teams that won games on wild-card weekend, Seattle was the only visiting team to walk away victorious.
Griffin was wearing a brace on the knee because of a ligament sprain he had suffered in December, one that sidelined him for 11/2 games. Further, he had tweaked the knee on a pass in the first quarter, and he wasn't his typical speedy, graceful self after that.
While the Seahawks are moving on to play at Atlanta in a divisional game, the Redskins are heading into the unknown, with their star player limping and questions about the judgment of their coach — why did Mike Shanahan keep him in the game? — that won't soon go away.
In a league that preaches that the health and safety of players is paramount, the injury to Griffin was a nationally televised example of how words and deeds are not always in lock step. Shanahan sounded conflicted as he spoke to reporters after the game, not knowing the severity of his quarterback's injury.
"I talked to Robert throughout the whole game, trying to get a gut [feeling], trying to let him know that it was all right if he was injured, that there was nothing wrong with that," the coach said. "But you've got to do what's best for the football team. [He was] very strong, very adamant. Doesn't mean you're right in not taking him out, I'm just saying that his personality has that type of mind-set. . . . You appreciate that toughness."
In an eye-opening revelation that surfaced before the game, Dr. James Andrews, a renowned surgeon, told USA Today that he had never cleared Griffin to return to the Dec. 9 game against Baltimore, when the quarterback was first injured. In the immediate aftermath of that injury, Shanahan told reporters that Andrews, who was on the sideline, had given his blessing to Griffin's reentering.
Griffin limped off the field for one play that day, then returned for four before leaving again when it was clear he couldn't continue.
After Sunday's game, Shanahan clarified the situation from the game a month earlier.
"At that time, I looked over at Dr. Andrews and he said, 'Yeah, he's OK to go back in,'" Shanahan said. "Of course, I'm sitting there trying to evaluate [backup quarterback] Kirk Cousins and our plays, so if somebody says, 'He's OK.' Well, what Dr. Andrews was talking about, and I talked to him today, he said, 'Hey, Robert came around, he started showing us that he could run. He was sprinting around, and then he just took off. I figured he was OK. I hadn't gone through a thorough examination until after the game.'"
To his Redskins teammates, Griffin's stubborn inability to remove himself from the game until he absolutely couldn't continue was a testament to his toughness and dedication, and an example of the widespread ethos in a sport in which there's always someone over your shoulder who's angling for your job.
Asked if players are willing to mortgage their futures to stay on the field now, Redskins tight end Logan Paulsen said: "It's hard to keep that perspective, I guess. Because in that moment you're like, 'I don't want to let anybody down. I don't want to let the team down.' It's hard.
"I feel like in some ways coaches need to help a guy like that to say, 'Hey, let's live to fight another day.'"