Washington Redskins survive the loss of rookie QB Robert Griffin III and pull off a last-second comeback, keeping playoff hopes alive with flair. (The Washington Post)

The Washington Redskins’ post-bye week surge and quest for the playoffs continued for another week Sunday, but this time with even more dramatic flair, as the team survived the loss of star rookie quarterback Robert Griffin III and pulled off a last-second comeback to beat the Baltimore Ravens, 31-28.

With Griffin on the sideline nursing what was called a sprained right knee, his backup, rookie Kirk Cousins, led the Redskins on the game-tying drive, throwing a touchdown pass to wide receiver Pierre Garcon, then rushing for a two-point conversion with less than a minute left in the game. Rookie Richard Crawford then ripped off a huge overtime punt return and first-year kicker Kai Forbath nailed a 34-yard field goal for the win.

Behind five rookies — Griffin, Cousins, Crawford, Forbath and running back Alfred Morris — the Redskins notched their fourth consecutive victory and improved their record to 7-6. It marks the first time since 2008 that the Redskins have orchestrated such a win streak, and the first time since that year that the team has owned a record above .500 in December.

“It’s a big game for us. . . . We knew if we didn’t get the win today, obviously, those other three [victories] didn’t mean a whole lot,” said Redskins Coach Mike Shanahan, who in two previous seasons had managed only six and five victories, respectively. “I’m really proud of the way the guys played.”

Team spokesman Tony Wyllie said Sunday evening that Griffin underwent an MRI exam and “everything is clear.” Griffin did not tear his anterior cruciate or medial collateral ligaments, Wyllie said, calling the injury a knee sprain and adding that Shanahan will provide further details Monday. It remained unclear whether Griffin will be able to play next weekend.

Said Robert Griffin Jr., Griffin’s father, in a text message to a reporter: “Knee better than yours and mine.”

Griffin suffered the injury with less than two minutes left in a game that the Redskins dominated in the early going, jumping out to a 14-7 lead on a Josh Morgan touchdown catch and Morris’s touchdown run in the first quarter. Washington accumulated 186 yards of offense in that quarter, more than any NFL team in the first quarter this season.

But the Redskins’ offense went cold for the better part of the next three quarters, generating just two Forbath field goals — from 48 and 49 yards — in the third.

After falling behind 28-20 on a seven-yard touchdown run by Ravens running back Ray Rice with 4 minutes 52 seconds left in regulation, Washington got the ball at its own 35. The team dodged a bullet when returner Niles Paul fumbled on the runback, and Baltimore’s David Reed appeared to recover as he slid out of bounds. But the replay showed that he bobbled the ball, and Washington took over.

Seven plays later, facing second and 19 at their own 27 with 1:56 left, Griffin took off and gained 13 yards. But as he was tackled, Baltimore’s Haloti Ngata drilled Griffin, whose knee appeared to hyperextend.

Griffin was helped to the sideline and watched as Cousins threw an incompletion, but a pass interference call on the play gave Washington new life. Griffin came back in and completed two of his next three passes, but went to the ground again after the fourth play — an incompletion and intentional grounding call — and Cousins came back into the game.

It was only the second game action of the season for Cousins, who beat out veteran Rex Grossman for backup duties and last played late in Washington’s Week 5 loss to Atlanta, when Griffin sustained a concussion.

Unlike that game, in which Cousins threw two interceptions and a touchdown in a loss, the fourth-round draft pick out of Michigan State answered the call. Cousins connected with wide receiver Leonard Hankerson on second and 20 for a 15-yard pickup, then found a wide-open Garcon in the end zone with 29 seconds left. On the next play, Cousins caught the Ravens off guard, scoring two points on a quarterback draw play that forced overtime.

Baltimore won the toss. But the Redskins defense held and the Ravens had to punt.

Then it was time for Crawford, a seventh-round pick out of SMU, to provide the heroics. Inactive for the past seven games after struggling as the team’s nickel cornerback, Crawford earned a chance to contribute on special teams after coaches grew tired of the ineffectiveness of return man Brandon Banks. Crawford, who had recorded returns of 20 and 16 yards earlier in the game, fielded Sam Koch’s punt and ran it back 64 yards to the Baltimore 24-yard line.

“I just saw daylight, and just ran to daylight,” Crawford said. “I knew we’d won because I had the confidence in Kai to make those. He hasn’t missed one since he’s been here, and I followed him in college, too, so I knew he could make them. I know he’s a very good field goal kicker.”

After running two plays, Washington sent on Forbath for the game-winning kick, and the first-year player delivered, hitting his 14th consecutive field goal as a Redskin.

“It was huge, huge win for our team,” said Forbath, who went undrafted out of UCLA last season and was on injured reserve with Dallas before signing with Washington before the sixth game of this season. “I was telling [punter] Sav [Rocca] that a lot of NFL games come down to field goals and we hadn’t had one, so I kind of had a feeling today was going to, and it did. Fortunately, we came out on the right side of it.”

After their hot start, the Redskins fell behind, 21-14, at halftime. The defense yielded three touchdown passes and was gashed by the Ravens’ rushing attack.

Takeaways on consecutive third-quarter defensive stands gave the Redskins new life, however.

Outside linebacker Rob Jackson rushed Baltimore quarterback Joe Flacco from his blind side and stripped him of the ball on the Ravens’ first possession of the second half. The Redskins went on to pull within 21-17 on Forbath’s 48-yard field goal.

After allowing the Ravens to march 54 yards to the Washington 11-yard line, the defense buckled down once again. On third and six, Jackson’s counterpart, Ryan Kerrigan, came untouched and hit Flacco as he let go of the ball, and inside linebacker London Fletcher picked off the pass.

Washington put together another drive, but came up short by a yard on third and seven at the Baltimore 36. Forbath then made the 49-yarder to trim the lead to 21-20 with 1:21 left in the third quarter.