LANDOVER, Md. — After taking a shot to his helmet while scrambling to try to avoid a sack, Washington Redskins quarterback Robert Griffin III stayed face-down for a few moments Sunday, then eventually staggered to his feet with what doctors determined was a concussion.

For Griffin, also treated for a cut on his chin after the third-and-goal play, the game was over about 10 minutes into the second half of Washington's 24-17 loss to the Atlanta Falcons.

Exactly the sort of thing everyone around the Redskins has been worrying about with the aggressive, never-avoid-a-hit Heisman Trophy winner.

"He wasn't sure what quarter it was in the third quarter. So at that time, when he wasn't really sure what the score was, what the quarter was, we knew he had a mild concussion — at least according to the doctors," Redskins coach Mike Shanahan said after his team fell to 2-3. "It feels good right now; a lot better right now. But that was ... why he didn't go back into the game."

Team spokesman Tony Wyllie said Griffin was examined by a neurologist in the locker room before being sent home from the team's stadium and will be evaluated again Monday. NFL rules require a player diagnosed by the team medical staff with a concussion to sit out the rest of the game. The player also can't return to practice or game action until a team doctor and independent neurologist clear him.

Griffin was not in the locker room after Washington's eighth consecutive home loss, but about three hours later, he wrote on Twitter: "I'm ok and I think after all the testing I will play next week."

The Redskins announced in the press box during the game that Griffin was "shaken up" and his return was "questionable" — and never updated his status. NFL spokesman Greg Aiello said the league would look into whether the Redskins followed a league requirement that teams are accurate and timely in reporting injury information.

"I knew it was a big hit, and I knew after he laid down that something was wrong," Redskins running back Alfred Morris said. "So I was like, 'Oh, no.' I said a prayer for him."

Said Redskins linebacker Lorenzo Alexander: "Obviously, it's a scary situation. Hopefully he's able to recover. Never want to rush a guy back like that. ... Hopefully Robert's able to get back as quick as possible — but only when he's completely healthy. Because once you get one concussion, they can occur rapidly if you go out there too soon."

Near the Falcons' sideline while trying to find someone to throw to in a 7-7 game, the No. 2 overall pick in this year's draft fell forward while being tripped up by one defender. Griffin's helmet slammed into the side of Falcons linebacker Sean Weatherspoon.

As Griffin was led off the field by trainers, chants of "RG3! RG3!" rang out in the stands.

"I felt like he was still turning upfield, so I was just trying to make a play. Most quarterbacks would probably slide out of bounds or run out of bounds, but he's a tough guy," Weatherspoon said. "He's a tough guy, and I think he'll learn a little bit."

Griffin's injury came on an afternoon when his running had been scaled back.

Through Week 4, thanks in part to using some option plays, he was the league's top rushing QB, with 234 yards, and already had tied a Redskins season record for a quarterback with four TDs rushing.

But against the Falcons (5-0 for the first time in franchise history), Griffin's only run was a 7-yard gain on a scramble. He was 10 for 15 for 91 yards throwing.

"It's a different dynamic when he's not in there. You don't have to account for the quarterback running the football," Falcons coach Mike Smith said. "He's a distributor who throws it and hands it off to someone else, so it did it change our game plan when he left the game."

On the play after Griffin was injured, the Redskins took a 10-7 lead on a 23-yard field goal by Billy Cundiff, who had missed four of his five previous kicks, including pushing a 31-yarder wide right in the second quarter Sunday.

Another rookie quarterback, fourth-round pick Kirk Cousins, took over for Griffin on Washington's next possession.

"I did get a word from a trainer that I would be going in and I would be finishing the game," Cousins said.

On his first snap in the NFL, Cousins completed a 4-yard pass to Joshua Morgan, before the Redskins wound going three-and-out and punting. On Cousin's second drive, he completed a 77-yard touchdown pass to Santana Moss to give Washington a 17-14 lead. But Cousins was intercepted on each of Washington's final two possessions.

The Redskins would like to see Griffin back under center next week against the visiting Minnesota Vikings.

Perhaps with a slightly more cautious approach on plays like the one that sent him to the sideline Sunday.

"You'd like to have him throw the ball away when he's outside the pocket and not have to take that hit like that," Washington linebacker London Fletcher said. "But he's a competitor, he's trying to make plays, so you can't fault him for that. But we're definitely concerned. Hopefully he'll be able to bounce back."