New York Giants defensive coordinator Steve Spagnuolo coaches against the...

New York Giants defensive coordinator Steve Spagnuolo coaches against the offense during training camp at the Quest Diagnostics Training Center in East Rutherford, N.J., on Friday, Aug. 7, 2015. Credit: Brad Penner

Steve Spagnuolo uses any number of tools to coach his defense: game tape, X's and O's play sheets, practice drills, blocking sleds, tackling dummies.

And, of course, the "relentless meter."

The rudimentary device is affixed to the board at the front of Spagnuolo's meeting room, and the arrow is adjusted on a daily basis. Practices. Games. Everything. Sometimes he'll use it to define an individual player's effort, or his defense as a whole. The higher the relentless meter reading, the better.

"That's kind of our thing, so I can't give too much away about it," Spagnuolo said with a smile after Thursday's practice.

Just how the dial is adjusted and who decides where to put it remains a bit of a mystery. By design.

"We didn't want the coaches to be involved in it, we wanted an outside eye,'' Spagnuolo said, "so it's kind of a subjective thing of evaluation, but it's helpful."

So who adjusts it?

"I can't reveal that," he said. "It's adjusted based on the information and on the game."

It's just another of the simple gimmicks from Spagnuolo that have his players believing in him. Rehired by Tom Coughlin after a resoundingly successful run with the Giants in 2007-08, which included a Super Bowl championship, the guy they call "Spags" is working more of his magic in running a far different defense than the one he left behind.

The relentless meter is further proof of his immediate influence.

"It's basically a symbol to make sure guys are flying to the ball at all times," linebacker Mark Herzlich said.

"You want it when every single person is pushing as hard as they can through the entire play. Harping on that has made a difference."

The results are starting to pay off. After two losses to open the season, the defense has been at the heart of back-to-back wins over Washington and the Bills. There's still a ways to go, and there's no telling if the absence of pass rusher Jason Pierre-Paul ultimately will doom the defense's chances of becoming dominant, but at least it is giving this team a chance.

And it's why Spagnuolo needs to rely as much on relentless play as the guile used in his imaginative schemes.

"That's what defensive football is all about, being relentless," Spagnuolo said. "To the players' credit, they've bought in. They've embraced it."

No one will ever mistake this Giants' defense with the great ones of the past. Not the defense once presided over by Michael Strahan, Osi Umenyiora and Justin Tuck. Or the one Lawrence Taylor, Carl Banks and Harry Carson used to dominate. Or the one from a bygone era that featured Sam Huff, Andy Robustelli and Jim Katcavage.

But if this year's unit, which is short on big names and sheer talent, continues to flourish on the merits of its grit and determination, its greatness will rest with the man who's supervising it.

Spagnuolo's schemes already are showing the kind of adaptability needed from a group with no stars and a limited pass rush. But it's also his unique ability to relate to his players and get them to buy into his system. Not just the X's and O's, but the attitude.

"I love his mentality, and we're starting to emulate it as a defense," said linebacker J.T. Thomas, who made a potentially game-saving tackle of Bills running back Karlos Williams on fourth down at the Giants' 1 in the fourth quarter on Sunday. "He's very aggressive. He makes things clear for you. More than anything, he's made things very flexible for us. "

Veteran safety Brandon Meriweather calls Spagnuolo "a rare student of the game who happens to be a coach." There will be no gaudy numbers created by Spagnuolo's defense, not without the star power he had in his previous incarnation with the Giants. But what the Giants lack in talent, they make up for with hustle.

And the arrow on the "relentless meter" always will let them know if the effort is good enough.

"If things aren't going exactly as they're supposed to, you can make up for a lot of mistakes just by being relentless," Spagnuolo said. "If we can keep doing that, we're halfway there."