EAST RUTHERFORD, N.J. -- One week, the Giants shut down the 49ers.

The following week, the Redskins are tallying near 500 yards on them.

It's the inability to stretch together solid outings that's keeping the Giants from being a top defense.

"We're not consistent," Giants defensive coordinator Perry Fewell said Monday. "We've shown at times that we can be a good defense, but we're not a consistent defense. That's what we're striving for: to be a consistent defense. I think that if we can obviously pull together, which we will, and be more consistent with what we do, that we can finish strong."

Fewell, who has been the team's defensive coordinator since 2010, said some of the consistency issue stems from personnel changes. The Giants have a new starting corner this year in Prince Amukamara, and safety Stevie Brown, who is replacing the injured Kenny Phillips, is in his first year with the team. An injury to linebacker Jacquian Williams has also limited the team in what it can do with its packages.

Perhaps a bigger reason for the inconsistency, though, is the amount of big plays the Giants yield. For the season, the Giants have allowed nine touchdown passes of at least 25 yards. In their final two games before the byes, both losses, long touchdown passes swung the game.

In the 24-20 loss to Pittsburgh on Nov. 4, the Giants surrendered a 51-yard touchdown to Mike Wallace that gave Pittsburgh life in the fourth quarter. Last Sunday against Cincinnati, a coverage mistake by Stevie Brown, as well as Corey Webster not recognizing the error, left A.J. Green wide open for a 56-yard touchdown in the first quarter that the Giants never seemed to recover from.

"In this league you have to make plays, and players have to make plays, and we as coaches have to put them in position to make plays," Giants defensive backs coach Peter Giunta said. "It's a little frustrating for them and us that we've been in position and we haven't been making those plays."

Giunta also raised the issue of tackling, pointing out how the team had several opportunities to make the tackle but whiffed on Wallace's touchdown. The Giants had 12 overall missed tackles in that game, including a handful on backup running back Isaac Redman.

Safeties coach David Merritt said when players are preparing to make tackles they need to know where their help is, but can't become too reliant on that help because that leads to what he calls a "passive" type of tackling. He wants his players to visualize that they are the only thing standing between a score.

"Tackling is always an issue in the NFL, not only with the Giants but everybody has a lot of missed tackles," Merritt said. "Especially when you get into November and December, some of these guys don't really want to wrap up and get physical. That's one thing we preach more over the past couple of weeks is that you have to tackle in November and December in order to win football games."