ASHBURN, Va. >> It doesn’t sound good for Robert Griffin III.

An injury that sidelines RG3 well into next season is a very real possibility — or at least it seemed that way Monday after coach Mike Shanahan described the results of tests on the rookie’s right knee.

Shanahan said the results are prompting the team to send Griffin to Florida on Tuesday to see renowned orthopedist James Andrews for more examinations, essentially a second opinion that will decide the team’s fate for the 2013 season.

“There is a concern,” Shanahan said. “That’s why he’s going to see him.”

Griffin tore his ACL while playing for Baylor in 2009, and Shanahan said that old injury caused Griffin’s latest MRI to prove inconclusive and produce “differences of opinion” in those who have looked at it.

“They want to take another look and have a physical exam with him,” Shanahan said, “to make sure they’re not looking at old injuries.”

A torn ACL typically requires a rehabilitation period of nine to 12 months, although some players don’t return to full health until their second season after the injury. On the other hand, one of this season’s most remarkable stories was Adrian Peterson, who returned about eight months after tearing an ACL and nearly broke the NFL’s single-season rushing record.

Notably, Shanahan referenced Peterson on Monday, pointing out that the Minnesota Vikings back had the big season without the benefit of an offseason practice program. It could be a possible scenario for Griffin.

Shanahan was grilled about his handling of Griffin’s injury. Already playing with a heavy black brace in his third game since spraining a lateral collateral ligament, Griffin hurt the knee again when he fell awkwardly while throwing a pass in the first quarter of Sunday’s 24-14 playoff loss to the Seattle Seahawks.

Griffin stayed in the game, but he was far from his usual self, clearly favoring the knee and unable to run with the world-class speed that helped define his play early in the season.

Then, in the fourth quarter with the Redskins trailing by seven, the knee buckled the wrong way when Griffin tried to field a bad shotgun snap. The Seahawks recovered the fumble deep in Washington territory, setting up a short field goal that helped put the game out of reach. Griffin was done for the evening.

Shanahan said he thought he made the “right decisions” to keep Griffin in the game and that it would be “crazy” to think he would purposely sacrifice Griffin’s career to win a game. He said he did not talk to team doctors initially after Griffin was hurt in the first quarter, instead relying on Griffin’s word.

“I went up to Robert. I said, ‘You OK?'” Shanahan said. “And he said, ‘I’m fine.'”

Griffin was also feeling the criticism for not taking himself out. He did not appear in the locker room during the two hours it was open to reporters Monday morning and instead made his public statements via Twitter.

“Many may question, criticize & think they have all the right answers. But few have been in the line of fire in battle. … I thank God for perspective and because of that I appreciate the support from everyone. I also appreciate the criticism. … When adversity strikes you respond in one of two ways….You step aside and give in..Or you step up and fight,” Griffin tweeted.

Teammates defended Griffin’s desire to play hurt, saying it’s part of an athlete’s competitive nature.

“It’s a slippery slope, I guess you can say, because you want to help the team,” said receiver Pierre Garcon, who faced a similar dilemma this season while dealing with a painful toe injury. “But you want to help yourself in the long run and your career.

“You want to look out for all sides, but it’s hard to really know exactly if you’re doing the right thing because if you sit out and the team losses, it’s like ‘I could probably have helped.’ If you go out there and don’t help the team, it’s like, ‘I probably should’ve sat out.’ You’ve just got to make a decision and live with it.”

Shanahan’s take on Griffin was also muddled by details that have emerged from the game in which the quarterback originally hurt the knee last month against the Baltimore Ravens.

The coach said at the time he was told by Andrews on the Redskins sideline that Griffin was cleared to return to the game, but Andrews told USA Today over the weekend that he didn’t get a chance to examine the knee during the one play Griffin sat out after the initial injury.

Shanahan explained the apparent discrepancy.

“I don’t sit down with him and say, ‘Hey, did you give him a proper evaluation?'” Shanahan said. “I ask him, ‘Is it OK if he goes back in the game?’ He says yes or no. He said yes.”

Either way, the various versions of what happened cast more intrigue on the protocol NFL teams use to determine whether someone is fit to keep playing. Redskins left guard Kory Lichtensteiger had to leave Sunday’s game in the first quarter because he could no longer play on a sprained left ankle that kept him out of practice all week.

“I went out there,” Lichtensteiger said. “But, in hindsight, I probably shouldn’t have done it.”

Griffin’s injury and the playoff loss put a damper on the end of one of the best Redskins seasons in two decades. Washington rallied from a 3-6 start to win the NFC East after four straight last-place finishes. Assuming Griffin’s knee will again be fully healthy, the future looks brighter than at any time since the Super Bowl era under coach Joe Gibbs in the 1980s and early 1990s.

“I think people have really learned around here — if you’re down by seven, people aren’t packing it in,” said safety Reed Doughty, wrapping up his seventh season in Washington. “People aren’t getting that ‘Oh, the way things used to be’ kind of feeling.”