Jim Schwartz talks like a head coach. The Eagles defensive coordinator, of course, has been there and done that, and would likely want another shot at leading an NFL team.

But Schwartz wasn't brought to Philadelphia to be the head coach. And that is something that he has been cognizant of since he was hired on the day the Eagles officially introduced Doug Pederson. He has mostly kept a low profile, and when he has spoken, he has been deferential to his boss.

Schwartz entered some tricky terrain on Tuesday, though. Asked about his experiences as a first-time head coach in Detroit with a rookie quarterback who was a first-round pick - just like Pederson and Carson Wentz - Schwartz reverted to head coach mode. Old habits die hard.

"Don't judge him on somebody else, and then also don't predetermine the results of the race," Schwartz said of Wentz. "Just let him go play. Don't put pressure on him."

It was innocent enough, and for someone who seeks truth, refreshing. But Schwartz would have been better off deflecting a question about the other side of the ball, especially when it was about the single most important player in regard to the franchise's future. He eventually did.

"I can't speak for Carson and what's going on. I have my own worries," Schwartz said. "You guys saw how crappy a practice that was. We've got enough worries on defense right now."

Some former head coaches can drift into the background as a coordinator or an assistant, especially if a first-time head coach requires it. Some can't. They're alpha dogs, and by their nature they can't help but overshadow lesser personalities.

Schwartz, by most descriptions, has a dominant personality. He did coexist with first-time head coach Doug Marrone in Buffalo, but it was for only one year before Marrone opted out of his contract. And only one of them was carried off the field that season - Schwartz, after the Bills beat his former team, the Lions.

It harked back to Super Bowl XX, when Bears defensive coordinator Buddy Ryan was, along with head coach Mike Ditka, hoisted by his players. Defense is often as much about state of mind as scheme, and fiery coordinators, when used properly, can motivate purely on emotion.

Leodis McKelvin, who signed with the Eagles this offseason, was one of the Bills players who rallied around Schwartz in Detroit two seasons ago.

"If you do something he doesn't like, that's when you're really going to see Jim get red with spit coming out of his mouth," McKelvin said. "But that's the type of coach you love playing for. If a coach is being straight with you and not showing you no kind of shade, you want to give a guy like that your all."

Schwartz's opinion of Tuesday's practice was accurate. The Eagles defense was sloppy. There were several false start penalties, missed assignments, personnel grouping mistakes and poor calls. All you had to do was watch Schwartz and listen to him to know he wasn't satisfied.

And the more he pressed his players, the more they responded, even though they were wearing only shells and contact is to be limited during organized team activities.

"As big as everybody thinks his ego is . . . he's actually very, very flexible," safety Malcolm Jenkins said. "He'll take criticism from players. . . . The mentality of the defense is more important than the X's and O's."

Schwartz's scheme isn't a complicated one. There will be an adjustment period as the Eagles reverse course and return to a 4-3 "under" defense after three years as a two-gap 3-4. But there aren't nearly as many responsibilities for linemen, and that is all by design. It's attack football. See ball. Go get ball.

"It's a coach's job to make a complex game simple for the players," Schwartz said. "It's our job to make it where they can digest it."

The scheme was originally designed with the Titans to take advantage of Jevon Kearse's skills as a rush end. Schwartz started out as a defensive assistant in Tennessee before eventually becoming coordinator. A successful eight-year run in that post led to the Lions job.

Schwartz had only one winning season out of five, but he inherited an 0-16 team and had to start from scratch with rookie Matthew Stafford at quarterback.

"Was he our best quarterback? Was he ready?" Schwartz said. "Unfortunately, he got hurt both his first and second year, probably from holding the ball a little too long at times."

The Eagles have opted to sit Wentz initially. They have far more talent than Schwartz had in Detroit. The expectations for the defense may be as high as they've been since Jim Johnson was coordinator.

Schwartz had obvious influence on personnel, with McKelvin and fellow former Bills Nigel Bradham and Ron Brooks being added this offseason. The Eagles also invested heavily in safety by signing Rodney McLeod and extending Jenkins' contract, and up front by retaining defensive end Vinny Curry. A new deal for all pro defensive tackle Fletcher Cox is likely forthcoming.

But Schwartz, who spent a year away from coaching working in the NFL's officiating department, preached patience.

"I think if you prejudge anything and say this is what's going to happen, I think you're on the wrong track," Schwartz said. "You've got to keep an open mind. It's hard to be patient in the NFL. But you have to be patient this time of year."

Schwartz turns 50 next week, so he has plenty of time if he wants to return to head coaching. Can he be patient? Can Jeffrey Lurie be patient with Pederson? The new coach doesn't have to look far if he wants a resource.

"He doesn't have very much of an ego," Schwartz said of Pederson, "and he's open-minded."

They could complement each other. Or their differences could be highlighted and they could be miscast. Time will tell. Patience.

jmclane@phillynews.com

@Jeff_McLane