GREEN BAY, Wis. (AP) Eddie Lacy understands why he has been demoted on the Green Bay Packers depth chart.

The next step for the third-year running back is to figure out why his slow start has turned into a season-long slump.

Coach Mike McCarthy tabbed James Starks as the Packers' top back going into this weekend's game against the Lions, replacing Lacy.

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''I would say James is our No. 1 back right now going into Detroit,'' McCarthy said Wednesday. ''He's played very well. He's earned that opportunity.''

McCarthy said he will continue to use both backs extensively. It's just that now Lacy is considered the backup.

''Because he's been the better player between us two so far,'' Lacy said after practice when asked why McCarthy made the move.

A traditionally slow starter, Lacy's extended slump has played a role in the offense's choppy production in the first half. Run blocking has also been an issue, both up front and in the secondary level, McCarthy said.

''It's not just one guy. If it's just one guy, we would've made an adjustment or a change already,'' McCarthy said.

Still, Lacy's dropoff has been a surprise since he ran for 1,100 yards in each of his first two full seasons in the league. Lacy has just 308 yards rushing on 83 carries in eight games this season.

He sprained an ankle in Week 2 and left Sunday's loss at Carolina with a groin injury. Lacy returned to practice on Wednesday on a limited basis.

The ankle, Lacy said, was fine, while the groin was feeling better.

The stats show why Starks has been promoted.

Lacy ran for 10 yards on five carries against Carolina's tough defense, while Starks had 39 yards rushing on 10 attempts. Starks also made an impact in the passing game with six receptions for 83 yards and a 29-yard touchdown in the fourth quarter.

Starks for the year has 334 yards rushing on 78 carries, but his 41.8 yard-per-game average is still three yards better than Lacy's average.

A reliable backup through most of his six-year career, Starks does have some familiarity with the starting job. As a rookie, he was the starter in the postseason when the Packers won the Super Bowl in 2011.

''I've just got to be ready if that's what coach wants me to do,'' he said. ''If I've got to be behind Eddie that's what I'll do. I'm a team player.''

There are no hard feelings in the running back room. Lacy and Starks joked around together and interacted on Wednesday as if their roles were not reversed.

''Everything is not going to go in your favor all the time. I think mistakes and things that happen in the game, it builds character,'' Starks said. ''He's going to do what he has to do.''

Lacy just has to figure out what that is.

A few weeks ago after studying tape, Lacy noticed that he was running too high. He adjusted and made a concerted effort to get his pads lower to get more leverage.

That didn't work in terms of yardage.

''I still broke tackles, but the production just wasn't there or how it used to be,'' Lacy said.

Ball security has been an issue as well, with three fumbles in three straight games after over the previous four seasons combined.

''What you can't do is allow something like this to ... play tricks on your mind, because then I think you'll just try to do too much and you'll be less productive,'' Lacy said. ''It's not like I'm just sitting the bench the whole time. So whenever I get in, I'll still try to do what I can for the team.''

NOTES: Top CB Sam Shields (shoulder) returned to practice on a limited basis, while CB Quentin Rollins (neck) was a full participant. Casey Hayward (concussion) sat out, while fellow CB Damarious Randall also missed practice because of illness. ... RT Bryan Bulaga, who missed three games earlier this year with a left knee injury, missed practice.

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