When the Green Bay Packers decided to pay premium dollar to keep Sam Shields (left) — $39 million over four years — this is the kind of matchup they had in mind. Calvin Johnson at Ford Field. Credit: Rick Wood

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Green Bay — Leaning against a table inside the Green Bay Packers locker room, Sam Shields stirs a bowl of chili. He takes a bite. He's in a very chill state of mind.

Relaxed, confident, this cornerback gets the stakes.

When the Green Bay Packers decided to pay premium dollar to keep him — $39 million over four years — this is the kind of matchup they had in mind. Calvin Johnson at Ford Field.

"Oh yeah, most definitely," Shields said. "Any game, they want to see that. So I'm going to give them what they want."

Will Johnson be alone on Shields Island all day? Hardly. Players say whoever's on "Megatron" will get help through Sunday's NFC North opener. But much like last year's meeting in Detroit, odds are it'll be the 5-foot-11, 184-pound Shields shadowing Johnson most often.

Sunday is an opportunity to justify the decision general manager Ted Thompson made in March.

Shields lauds Johnson as "a big target," a "beast." However, to him, he is not some immortal robot who cannot be stopped, as the moniker suggests.

"He can be stopped," Shields said. "You have to go in there with that mind-set that 'I'm here.'"

Shields' career arc has led to this challenge. As an undrafted rookie in 2010, as the cornerback struggling to tackle in 2011, he wasn't ready for the 6-foot-5, 236-pounder. Tramon Williams guarded Johnson, often with a safety cheating his way. In 12 games against Green Bay, Johnson has erupted for 71 receptions, 1,163 yards and 12 touchdowns. It's always relative. He only won two of those games, one with Aaron Rodgers on the field (for a half in 2010).

A year ago, a contract year, Shields got his shot. The Packers were embarrassed, 40-10, but Shields earned points at the negotiating table. Outside of three slant passes underneath for 46 yards, he battled. On one deep throw, he wrestled the ball away from Johnson for an interception.

There's a chance defensive coordinator Dom Capers could throw a Davon House-sized wrench into the Lions' plans. Possibly House's physicality is worth a look.

Shields, however, sounds like a player ready for the showdown. If it were up to him, he'd cover Johnson one on one all game, no help.

"There are going to be some one-on-one situations," Shields said. "Sometimes, there will be the other situation. Whatever the coach wants to do, I'm willing to go for it.

"He's a guy who's going to catch balls because he's a great receiver. It's just me going in with that mind-set that, 'Hey, he can't catch the ball.' Go in there with a DB mind-set — we're going to go at one-on-one."

Against Johnson, Shields continued, you must eliminate yards after the catch. He cannot gain a head of steam.

And against Shields, Johnson knows he's facing a cornerback who'll play the ball, citing the fact that Shields was initially a wide receiver at Miami. In four seasons, Shields has 13 interceptions and 46 pass break-ups.

"He is pretty sticky in coverage," Johnson said, "and he has good ball skills, so that's a good thing for a corner."

It's been an up-and-down start for Shields. At Seattle, he broke beautifully on a Russell Wilson pass that inside linebacker Brad Jones should have intercepted. Against New York, he was burned not so beautifully on a double move by Eric Decker for a 29-yard touchdown.

Complicating matters for Green Bay this week is the fact that the Lions' passing game is no longer a monopoly.

Golden Tate was signed to a five-year, $31 million contract to be everything the combustible Titus Young was not. Tight end Eric Ebron was drafted 10th overall. The names Reggie Bush and Joique Bell come up a lot in the Green Bay locker room. Coach Jim Caldwell said these additions all "tip the scales" to keep double-coverage off of Johnson. Then again, when the New York Giants single-covered Johnson, he went off for 164 yards and two touchdowns.

Even though it'd help if one cornerback could track Johnson much of the day, that's probably an unrealistic proposition.

"No, I don't think we'll necessarily put it on one guy to take care of Calvin Johnson," safety Micah Hyde said. "We're all out there helping each other. You have to know where he is. If you're on him, you have to know where the help is. There's a lot that goes into it. We're trying to simplify it as much as possible.

"A huge weapon, a great receiver, you just have to have a lot of respect for him."

You'll just see No. 37 and No. 81 in the same vicinity very often.

How far has Sam Shields come? The Packers are about to find out.

During the summer, Shields brushed off this whole NFL emphasis on illegal contact. Wouldn't affect his game, he said. His game is based on speed, footwork, timing — not hand-to-hand combat.

Ten years ago, cornerbacks might have been able to knock Johnson off the top of his route. Commissioner Roger Goodell and Co. put the kibosh on that.

Now, the Packers are hoping Shields (with help, of course) is the answer.

They paid him accordingly.

"I'm working on it day by day," Shields said. "It's getting better. Me as a DB, I'm still learning. I'm getting better at it. Throughout the year, it'll come."