Patriots middle linebacker Jerod Mayo, right, intercepts a fourth quarter pass from Rex Grossman with 22 seconds left in the game last weekend. (John McDonnell/The Washington Post)

The bookend plays of the Washington Redskins’ most recent loss to the New England Patriots also could bracket their season. In the first quarter, quarterback Rex Grossman dropped back to pass in his own end zone, was drilled by New England defensive end Andre Carter, dropped the football and yielded a touchdown. In the fourth quarter, trailing by just seven points, Grossman looked for veteran wide receiver Santana Moss inside the Patriots 5-yard line. The ball hit Moss in the hands, popped out the other side, and was intercepted.

Those were the 29th and 30th turnovers of the Redskins’ season, and they — more than any other plays — prevented Washington from winning, yet again. Only two teams — Philadelphia and Tampa Bay — have more turnovers, with 31 and 32, respectively. No team has a worse turnover margin than the Redskins, who have committed 14 more than they have created.

And this isn’t a new problem: The last time the Redskins went without a turnover was Sept. 19, 2010, 27 games ago. That’s the longest active streak in the NFL.

“This is almost every year,” said Redskins Coach Mike Shanahan. “If you look at the playoffs, the teams that don’t turn the football over, they usually win the Super Bowl. . . . If you look at turnover ratio, if you look at the teams that get in the playoffs, usually there will only be two or three that aren’t [among the best in the league]. That’s a big part of winning and losing.”

Perhaps the biggest. In 13 games this year, the Redskins — who face the New York Giants Sunday in East Rutherford, N.J. — have yet to create more turnovers than they commit. There is a direct correlation with their 4-9 record. The top five teams in turnover margin have a combined .785 winning percentage. The bottom five: .292.

For all the Redskins’ problems in what will be their fourth straight losing season — flip-flopping from Grossman to John Beck and back to Grossman at quarterback, the defense’s inability to stop opponents at crucial moments — many of the players will look back on these games and wonder: What might have happened if we had held onto the football?

Each turnover its own story

When Grossman prepared to take that ill-fated snap from center in the first quarter of last week’s game against the heavily favored Patriots, he hadn’t yet completed a pass, and the Redskins had managed a total of five yards in their two possessions. It was third and nine from their 5-yard line. In the shotgun formation, Grossman’s feet were on his own goal line.

Grossman believes that each turnover has its own story, that rarely are they the fault of one person. This season, he has had the opportunity to tell many tales. In 10 starts, he has thrown 16 interceptions. Only two players — Tampa Bay’s Josh Freeman and San Diego’s Philip Rivers — have thrown more picks. Of the 29 quarterbacks with more than 240 pass attempts this season, none has a higher interception percentage than Grossman’s 4.6.

“We’ve been competitive in most of our games that we’ve lost,” Grossman said. “It comes down to a play here or a play there and, I think, without a lot of those turnovers, maybe we can put ourselves in that situation where we dominate a team. We’ve got to figure out a way to finish those games that are tight. We also need to figure out a way to eliminate mistakes so we get a little bit of a cushion.”

When Grossman dropped back against the Patriots, to his left was Willie Smith, an undrafted rookie forced into action at left tackle, playing the third snap of his career.

“You find out that game speed is a little different than what you’re used to” Smith said. His job was to block Carter. Smith lunged at him, a no-no. Carter simply overpowered him, then ran around him.

“It’s a tough situation,” offensive coordinator Kyle Shanahan said. “He gets thrown in there. We’re backed up in the end zone. He definitely didn’t do a good job on that play.”

Any turnover could be broken down in such a manner. The Redskins have spent many Mondays — when the team goes over the mistakes from each loss, the most painful day in a losing team’s week — watching tape of such errors.

In Week 6, when Grossman threw four interceptions and the Redskins lost to Philadelphia by a touchdown, each pick had a different narrative. On one, tight end Fred Davis failed to run a route correctly, making the play easy for Eagles safety Kurt Coleman. In Week 10, after Grossman had wrested the starting job back from an ineffective Beck, he tried to loft a red-zone throw to wide receiver Leonard Hankerson, but Miami linebacker Karlos Dansby read the play perfectly. The interception turned a potential go-ahead touchdown into a game-clinching turnover.

“A lot goes into every play,” Grossman said, “good or bad.”

So though Carter beat Smith on Grossman’s fumble last week, there were others involved in the game-altering play. Grossman’s first look was to his right, where wideout Jabar Gaffney ran a pattern that was designed to come back to the quarterback. “They looked like they were squatting the route,” Grossman said, meaning the defensive back was essentially waiting for an interception, unconcerned about a potential deep ball. So he turned to his next option, slot receiver Moss over the middle. That’s when he made a game-changing mistake.

“In that situation, with where we were and the timing of everything, I just need to throw it away,” Grossman said. “Not go to number two, just go to number one and just get rid of it and punt. Live to play another series.”

Instead, after Grossman had held the ball for 3.1 seconds, Carter got to his blind side, hit him hard and stripped the ball. Patriots defensive lineman Vince Wilfork recovered it for New England’s first touchdown. It was the Redskins’ 29th turnover and the 19th of Grossman’s season, counting fumbles and interceptions.

“Rex could’ve saved [Smith] if he got rid of it earlier,” Kyle Shanahan said. “Willie could’ve saved Rex if he blocked him just a little bit better. That stuff happens.”

To the Redskins, it happens every week.

‘Don’t fix it, you don’t win’

A year ago, as the Giants went 10-6 but missed the playoffs — a year in which one more win would have meant a postseason berth — no quarterback threw more interceptions than New York’s Eli Manning, who gave the ball away 25 times.

“A turnover can cost you a football game,” Giants Coach Tom Coughlin said this week. “. . . Other than points for-points against, the number one stat in the NFL is the takeaway-giveaway margin.”

As their game against the Redskins approaches, the Giants (7-6) are once again living on the edge of the postseason. Their running game, shockingly, is the least productive in the league. Only two teams allow more yards per game. Still, if they win their last three games, they will be the NFC East champs. One reason: Manning’s interception percentage has dropped from 4.6 to 2.5 percent. He has thrown only 12 interceptions.

“He’s committed to that particular aspect of the game and trying to do the best that he can, and he’s done a good job of throwing the ball away,” Coughlin said. “. . . Rather than always being inclined to try to fit those tight balls in there, he’s throwing some away this year.”

Grossman and the Redskins haven’t made that adjustment. Since their last Super Bowl victory following the 1991 season, the Redskins have committed more than 30 turnovers five times. With three games remaining, this year’s team isn’t likely to match the 40 turnovers of the 1994 and 2002 squads, but it easily could surpass the 2000 team — which had 33 — to total the second-most over the past two decades.

None of Shanahan’s 14 teams in Denver turned the ball over more than 32 times. Three more turnovers over the last three games and Shanahan will reach a new personal high.

As he considered the problem this week, Shanahan ticked off the games that might have been different had the Redskins taken care of the ball. Two losses to Dallas by a total of five points. The loss to the Eagles. Others to the New York Jets and the Patriots. He all but rolled his eyes, because he knows one NFL truism.

“If you don’t fix it,” Shanahan said, “you don’t win.”