It's supposed to provide a boost to themselves and hurt a division rival at the same time. That's the benefit of signing a player from a team in your own division. The Redskins have done so in the past; they did it again this offseason -- twice.

First they landed defensive lineman Jason Hatcher, taking him away from Dallas. Then it was receiver DeSean Jackson from Philadelphia.

"It's always great to go to a division rival and take someone from their roster that was big for them and bring it to your own team," Redskins nose tackle Barry Cofield said. "That's almost a double whammy on their part."

How much does it really help or hurt? New York adequately replaced Cofield and won a Super Bowl in his first season with Washington. But the Giants' defense did fall in terms of effectiveness after he left, falling from 17th in points allowed his last season there to 25th the following year. Many reasons could explain that tumble and the Giants did rank 12th in points allowed in 2012. They survived the loss of a player to a division rival.

But consider that during Cofield's time in Washington, the Redskins steadily improved against the run while the Giants temporarily declined in this area. The Redskins went from allowing 4.6 yards per carry before Cofield arrived to 4.3 then 4.22 and finally 3.99 this past season. New York took an initial dip going from 4.16 yards per carry in his last season with the Giants to 4.46 and 4.6 in its first two seasons without him before rebounding this past season at 3.84.

Cofield has been a solid player for Washington, but its defense clearly needs more. The Redskins ranked 21st in points allowed the year before his arrival and have gone 21st, 22nd and 31st in points allowed with him. He has not emerged as the NFL's best nose tackle as the Redskins had once predicted.

And I use Cofield as an example more than Stephen Bowen, also signed from a division rival, because he was a full-time starter for all of his five seasons in New York. The most Bowen had started was nine games in 2010 for Dallas.

And the overall point is: They survived the loss of a player to a division rival. But the other point is: Cofield did help the Redskins' defense.

And 20 of his 95 tackles in Washington have occurred in six games against the Giants. That's 21.1 percent of his tackles during his 48 games with the Redskins. Yeah, those games probably meant something more. For Bowen, 11 of his 85 tackles -- or 12.9 percent -- and 1.5 of his seven sacks have come in five games against Dallas.

Cofield said playing your former team twice a season definitely matters.

"There's that chip you carry on your shoulder playing against your old team," Cofield said. "It's like playing against your brother in the backyard. You love them, but you want to beat them worse than anybody for bragging rights. Having guys within the division, having that hatred -- not just my feeling for the Giants, but my feeling against the Cowboys and Eagles built over the years. DeSean has feelings in the division that will be strong I'm sure. Playing against teams twice a year, you can't replicate it. So playing a division rival is a positive in many different ways."

The Redskins did not get the double whammy when they obtained quarterback Donovan McNabb from Philadelphia in 2010. Of course, that's exactly what the Eagles got as McNabb struggled, the Redskins went 6-10 in their one season with McNabb under center and they ended up with two draft picks. Oh, and they went 10-6 and made the postseason (but McNabb did win an ugly game in Philly; so he had that going for him). Then again, McNabb's failure eventually led to the Redskins' aggressive pursuit of quarterback Robert Griffin III.

Dallas and Philadelphia both were fine letting Hatcher and Jackson leave. The Cowboys weren't going to re-sign Hatcher and the Eagles cut Jackson. But having them both remain in the division? The Redskins hope they make their former teams pay.