The first glimpse of what the new-look Giants defense is supposed to resemble comes tonight in the preseason opener against the Panthers, for a brief time, that is.

Starters will go two or three series at Giants Stadium, likely exiting before the end of the first quarter. Defensive tackle Fred Robbins (calf) will not play and holdout Michael Strahan remains out of the picture.

Still, this is the debut, of sorts, of the unit first-year defensive coordinator Steve Spagnuolo now commands and excitement is rampant among the players in the new system.

“It’s going to put our rules and what we’ve learned so far in this defense to test,” linebacker Antonio Pierce said. “There’s going to be mistakes from a mental standpoint, but if we go out there and fly around and be physical, that’s what we’re looking for. There’s a different attitude, a different temperament by our defensive coordinator and guys are loving playing for him right now.”

A former Eagles assistant, Spagnuolo has never called the defensive shots as a coordinator. He realizes and embraces the increased responsibility.

“What will be exciting and new will be the actual game day, making the calls,” Spagnuolo said. “That will probably be the biggest difference and the most exciting thing. You’re a part of the game now. As an assistant coach, I always felt like by the time Saturday came I pretty much had done my job. I got a couple of little things I got to do on game day, but the bulk of my work was from Monday through Saturday.”

During the real season, Sundays will be the days of decision for Spagnuolo, who is extremely short in stature and makes his presence felt not by yelling but with constant commentary, most of it positive in nature. The defense is decidedly more aggressive (in theory) from the Tim Lewis scheme of the past few years and, predictably, more popular with the participants.

Lewis, coincidentally, will be in the building tonight, as he’s Carolina’s defensive backs coach.

“I think the biggest thing that Steve’s tried to emphasize for these guys is really have a downhill, attacking mentality,” said linebackers coach Bill Sheridan, a holdover from Lewis’ regime. “I know it might sound very trite, but he really just pounds ’em every day when we watch the practice film.”

This is a more finely-tuned chance to see how Mathias Kiwanuka is progressing at strong side linebacker after moving from defensive end. Free agent pickup Kawika Mitchell makes his debut at weak side linebacker, and James Butler, vaulted over last year’s starter, Will Demps, looks to cement his job with the first unit at strong safety.

Pierce knows the performance won’t be perfect and is anxious to see Spagnuolo in action. Lewis spent the game calling the defense up in the press box. Spagnuolo is expected to be down on the sideline.

“I’ll be interested in seeing how he responds, how he’s going to make the calls and adjustments, his whole demeanor, because everybody picks it up a notch, not just the players but the coaches,” Pierce said. “He’s different from the meeting rooms to the practice field and now here comes game day. I think what’s been good is everybody’s been feeding off the defensive coordinator, so it’s going to be interesting to see.”

As far as Spagnuolo working the game from the bench, that’s the way Pierce wants it.

“Most D coordinators I played with are on the field,” he said. “Sometimes when you’re the d-coordinator you’re relaying messages to the assistants, so it’s like you’re getting third party. They try to say it the best they can like him, there ain’t nothing like getting it from the horse’s mouth. The vibe, his energy, his emotions, it carries onto the players.”

paul.schwartz@nypost.com