Allen Park — Haloti Ngata is so large, you can't miss him, even when he's missing. There he is in the locker room, throwing bean bags in a feisty game of cornhole. There he is on his stool, munching popcorn, patiently insisting he's not worried about missing training camp and at least half the exhibition schedule.

Ngata sits just about where Ndamukong Suh used to sit, in a corner of the locker room. And in much different ways than Suh — for instance, Ngata will chat pleasantly and goof around with teammates — he's the elephant in the room. (Note to Ngata: That's a comment on status, not size. I swear.)

In the midst of the Lions productive, tranquil camp, Ngata is the lingering question, still sidelined with a hamstring injury incurred in non-football activities. He did light work with trainers on the side during practice Tuesday, a positive sign. Coach Jim Caldwell and defensive coordinator Teryl Austin steadfastly refuse to be alarmed, noting Ngata is a 10-year veteran and five-time Pro Bowler with the Ravens, and knows how to get himself ready.

No one should be ringing any alarms — yet. It doesn't appear Ngata will play in either of the final two exhibitions, but Detroit is hopeful he'll be ready for the opener in San Diego. The Lions are understandably cautious with their 345-pound defensive tackle, and it's smart to save an experienced player for the real games. They're doing it with Calvin Johnson too, who might never play another preseason game, and probably shouldn't.

But whether this is strategy or injury circumstance, the Lions' defense won't be whole until Ngata plays.

"You don't want to rush it, because if you tweak it, then it's tweaked all season," Ngata said. "We're trying to figure out when would be the time to come in. We're just making sure I'm 100 percent before I do."

Ngata has been here since March, when the Lions acquired him in a surprising trade after they lost Suh. But in many ways, he hasn't really been here, absent from most voluntary OTAs, although he attended minicamp.

Frankly, the most important move for the Lions defense, ranked No. 2 last season, was keeping Austin, a terrific leader and play-caller who will get a head-coaching gig soon. Nine of 11 starters are back, but Austin already has been adjusting, setting linebackers and safeties loose on blitzes, generating pressure from multiple places.

Awaiting difference-maker

Players pledge wholehearted allegiance to Austin, and there are good defensive linemen on the roster. But even at 31, Ngata can be a difference-maker.

"I would love to see him, but if we don't, what are we going to do?" Austin said. "I'm not going to make the guy come out and practice when he's not ready. So we deal with it as it comes. I know Haloti and I know he'll be ready to play."

Caldwell has said he expects Ngata to be set for the opener, but dialed down some of the optimism recently. Ngata is switching from a read-and-react role in the Ravens 3-4 defense to an attacking role in the Lions 4-3 front.

Prudence is one thing, and it makes sense. Patience is another, and Ngata and the coaches have to be getting itchy.

"He's not ready to go, he hasn't been released (by trainers) yet," Caldwell said. "But I do think his return-to-play protocol is on time, and I think he'll be all right."

This is one of Caldwell's strengths, his connection with players and his respect for veterans. Caldwell was an assistant in Baltimore for two seasons with Ngata, and Austin was there as the secondary coach. Familiarity with the man isn't an issue. Familiarity with the system is the concern.

The Lions need Ngata, and not just because they lost their top two defensive tackles, Suh and Nick Fairley. Second-year tackle Caraun Reid has performed well, but now is out for an undetermined time with an ankle sprain. Newcomer Tyrunn Walker has been impressive at times.

The Lions are in good shape at defensive end with Ziggy Ansah and Jason Jones (returning from injury) but their other primary tackles are young (rookie Gabe Wright) or unproven (Jermelle Cudjo).

'That little spark'

When the Lions traded fourth- and fifth-round picks for Ngata, they knew they were getting a star on the back end of his career. His contract is up after the season, and before negotiations can proceed, they actually need to see him on the field.

Ideally, they'll see an established pro with a bit of a chip, somewhat miffed the Ravens let him go to free up salary-cap space.

"Yeah, you're kind of upset they couldn't figure something out with Baltimore," Ngata said. "Them trading you, it's kind of like them thinking you're older and washed up. So you have that little spark that gets you going again."

Teammates say Ngata already commands respect, and they can't wait to see his impact. With so many pieces still here from a powerful defense, there's no pressure on Ngata to dominate, and not much problem fitting in.

After a raucous cornhole game in the locker room Tuesday, Ngata playfully barked at his vanquished opponent, backup linebacker Travis Lewis, "Don't play me again! I'll embarrass you every time."

Ah, if only the transition to a new defense was so easy.

"It's not that simple at all, totally different terminology and technique," Ngata said. "Maybe we'll give it a go for the last (preseason) game. If not, we're just aiming for that first game. (Austin) does a great job with his scheme, keeping it likable and learnable. Right now, I can't play, but I'm not down at all."

Good to hear. For the Lions, it'll be much better to see.