ASHBURN, Va. — It’s unclear who will be at quarterback when the Washington Redskins visit the New York Giants this Sunday because Colt McCoy, the third-stringer turned favorite of first-year coach Jay Gruden, sprained his neck late in Sunday’s 24-0 shutout loss at the hands of visiting St. Louis.

“Their defense is good,” said McCoy, who was struggling before he was injured when sacked by Rams defensive end Robert Quinn midway through the fourth quarter. “We made them look really good. It’s the first time in my life I’ve ever been shut out. … I still played a few more snaps, but I just knew something wasn’t right. I’m not really sure what’s going on yet. That’s why we’re doing tests and meeting with the doctors.”

If McCoy isn’t recovered in time, Gruden said that he plans to start Robert Griffin III, whom owner Dan Snyder and general manager Bruce Allen joined with former coach Mike Shanahan in drafting after dealing three first-round choices and a second-rounder to the Rams for the second overall pick in 2012.

In fact, Gruden didn’t rule out starting Griffin at New York even if McCoy is cleared physically. Kirk Cousins is the other option but he had an awful game against the Giants at home in Week 4.

“We’re all searching for answers,” Gruden said. “We’re trying to find out who can lead us to victories and who can get this offense on a roll. That obviously is still to be determined.”

After Washington was manhandled in San Francisco in Week 12, Gruden said that he planned to stick with Griffin – who had returned from a dislocated ankle two weeks prior to that – only to reverse field after watching the film the next day.

McCoy’s injury adds an element of mystery to this week’s version of quarterback roulette, but Gruden clearly likes the former Texas standout, the only one of the three passers whom he brought to Washington. Hence the coach’s decision not to pull McCoy for Griffin with the Redskins trailing the Rams 24-0 late in the third quarter.

“As a coach, you don’t want to be wishy-washy,” Gruden said. “When a guy has a bad game, you just don’t want to take him out and throw him under (the bus). You like to see guys finish what they started and see if they can turn it around. Obviously that didn’t happen.”

Gruden neglected to mention that he had done that very thing to Cousins seven weeks earlier, yanking him in favor of McCoy with Washington trailing visiting Tennessee at halftime in Week 7. Cousins, who hasn’t played since, has mixed plenty of big plays with too many turnovers and has lost his last seven full starts since winning his first in place of the injured Griffin in Week 15 of their rookie seasons of 2012.

Griffin, whom Gruden benched for McCoy after three straight November defeats, was the NFL’s Offensive Rookie of the Year when he set records for passer rating and rushing yards by a rookie quarterback. However, he hasn’t been the same electrifying dual threat since his rookie year ended with a torn right ACL and LCL in the playoff loss to Seattle. He hasn’t started and finished a victory in 13 months, going 0-9.

“My focus is to help this team win … I’m not going to undermine anybody else,” Griffin said after his first career relief stint lasted all of five plays.

Griffin doesn’t have to undermine anyone. His teammates didn’t need any help in bumbling to a fifth straight defeat and a 3-10 record, the Redskins’ fifth double-digit losing season in six years.

Alfred Morris ran for 12 yards on his first carry, minus-6 on his other seven. The 2013 Pro Bowl running back has averaged 5.5 yards per carry and 101 yards per game in Griffin’s four full starts, just 3.4 per carry and 55 yards in Washington’s other nine games. The blocking was equally inept against the Rams’ pass rush, surrendering seven sacks, raising its total to 29 during the past five games. The Redskins are only the second team to give up at least six sacks in consecutive games in eight seasons. The other was the 2012 Cincinnati Bengals, whose offensive coordinator was Gruden.

“There’s really not a lot positive we (can say),” Gruden said about his offense, which never crossed the St. Louis 20-yard line. “We gotta figure out something that we do well.”

Against the Rams, that wasn’t playing defense — the unit, which allowed five plays of at least 30 yards the previous Sunday at Indianapolis, gave up three more — or covering punts. That unit was burned for returns of 28, 39 and 78 (the latter for a touchdown) yards by the Rams’ Tavon Austin, who came in averaging only 7.3 yards per return.

“Obviously we’re going down instead of raising our level of play,” Gruden said. “We have to figure out a way to stop the downfall and … rise somehow.”

NOTES: RB Roy Helu sprained a big toe during the fourth quarter against the Rams. Gruden said that the third-down back likely won’t play at New York. A similar injury derailed Helu’s 2012 season early so it wouldn’t be a surprise if he’s done for the year. … WR DeSean Jackson was inactive against St. Louis after badly bruising his lower right leg last Sunday at Indianapolis. Gruden is hopeful that Jackson will be ready this week. … S Brandon Meriweather was inactive against St. Louis after spraining a big toe at Indianapolis. Gruden said that Meriweather isn’t hurting as badly as Helu but that he’s questionable to face the Giants.

REPORT CARD VS. RAMS

PASSING OFFENSE: D — The Redskins allowed seven sacks, raising their total to 29 during the last five games. Coach Jay Gruden has put more of the blame the past two weeks on the backs and tight ends than the line, but left tackle Trent Williams hasn’t played up to his Pro Bowl standards. Williams and right tackle Tom Compton each gave up a bad sack against the Rams with the former’s coming on the play on which quarterback Colt McCoy sprained his neck.

McCoy, who came in with a 113.5 passer rating during his first 10 quarters, posted a 54.0 rating against St. Louis with two interceptions and just 199 yards on 32 attempts while generating no points. With big-play threat DeSean Jackson (legs) out, Pierre Garcon returned to the No. 1 receiver role, catching nine of the 11 balls thrown his way for 95 yards. No one else caught more than three balls for 43 yards. That includes Andre Roberts, who started in Jackson’s place but produced just 11 yards on two catches.

RUSHING OFFENSE: F — Alfred Morris is a Pro Bowl back, but he gained just six yards on eight carries against St. Louis for the worst game of his stellar three-year career. The holes certainly weren’t there, but Morris didn’t break any tackles either, once losing seven yards when swarmed by Rams defenders. McCoy and reserve back Silas Redd combined for 19 yards on three carries.

PASS DEFENSE: D — Giving up only 213 yards while registering four sacks wouldn’t normally justify such a low grade, but the Redskins surrendered catches of 35, 36 and 41 yards to the 26th-ranked passing attack. Rams tight end Jared Cook was wide-open on his touchdowns of one and 35 yards. St. Louis quarterback Shaun Hill didn’t blister Washington as much as Indianapolis’ Andrew Luck had the previous week, but Hill is a journeyman, not the league’s top young passer.

Outside linebacker Ryan Kerrigan raised his career-high, team-leading sack two more to 11.5. Outside linebacker Trent Murphy and defensive end Jason Hatcher combined for a sack and nose tackle Chris Baker added another but he was too busy celebrating on one of Kerrigan’s takedowns to notice the ball was next to him before the Rams recovered it. Safety Ryan Clark had a couple of big tackles but also committed a foolish personal foul. Phillip Thomas wasn’t much noticed in his first career start in place of the injured Brandon Meriweather (toe).

RUSH DEFENSE: C- — Washington’s run defense looked good by comparison to its pass defense although St. Louis churned out 131 yards on 30 carries. The Redskins kept Rams back Tre Mason — who had burned Oakland for an 89-yard touchdown the previous week — in check, but backup Benny Cunningham averaged 6.7 yards on three carries and receiver Tavon Austin dazzled them for 9.2 per carry on five runs. Will Compton was credited with a game-high 14 tackles in place of the injured Keenan Robinson (knee) while fellow inside linebacker Perry Riley had his best game in a while with 10 tackles, three of them for losses, one more than Clark recorded.

SPECIAL TEAMS: D- — Tress Way continued to boom punts, averaging 45.8 yards on six kicks, but the Redskins couldn’t control Austin, who had returns of 28, 37 and 78 yards, the latter for the game’s final touchdown. Meanwhile, Roberts produced just three yards on two punt returns although he did bring one of his four kickoff returns back 33 yards. Kicker Kai Forbath didn’t do anything except kick off to start the second half as McCoy threw interceptions to end his two drives into St. Louis territory while replacement Robert Griffin III’s lone series ended with a failed fourth down at the Rams’ 33. Way was stopped three yards shy of the first down when Washington went for it rather than punt on fourth-and-5, trailing 9-0 in the third quarter.

COACHING: F — The Redskins were minus their big-play receiver, their top tackler, their three-time Pro Bowl outside linebacker, their three-time Pro Bowl cornerback and one of their veteran safeties, but they were back home against a beatable Rams team. Instead, Washington came out listless and never rebounded in getting blanked in its own stadium for the first time in nearly five years. The offense was inept. The pass coverage let St. Louis pass-catchers run free. The punt coverage unit was awful and the fake punt didn’t work. This was certainly one of the worst days for coach/play-caller Jay Gruden, defensive coordinator Jim Haslett (who was blasted before the game by former captain London Fletcher) and special teams coordinator Ben Kotwica.