By Dan Duggan | NJ Advance Media for NJ.com

The new Giants general manager will have to make major decisions about the futures of quarterback Eli Manning and wide receiver Odell Beckham Jr. before he even has time to decorate his office.

But once those franchise-altering decisions are made, the new GM will really have to roll up his sleeves and get to work. The biggest challenge facing Jerry Reese's successor will be building an offensive line after years of neglect and poor investments.

There are no easy solutions, but here's a crack at how the Giants can start to rebuild their offensive line this offseason:

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The overall plan

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Andrew Mills | NJ Advance Media for NJ.com

The biggest change necessary has nothing to do with draft picks and free agent signings. The Giants first need to instill a sense of competition on the offensive line.

Bringing back the same five players this season from a bad offensive line was an inexcusable plan by Reese. Jobs can't be handed to under-performing players simply due to their draft status or contracts.

Offensive lines need to be gritty and that starts with fighting for jobs in the preseason. The new GM and coach need to foster a culture of competition throughout the roster, and especially on the offensive line.

Now, here's a position-by-position look at how to upgrade the offensive line:

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Center

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Andrew Mills | NJ Advance Media for NJ.com

I'm going to attack this process from easiest-to-toughest. To me, the decision at center is a no-brainer.

The solid play of Brett Jones since taking over at center in Week 5 saved the Giants a tough call and some money. Entering the season, it looked like they'd have to decide if Weston Richburg was worth top dollar. But Richburg's inconsistent performance and the concussion that ended his season prematurely should make it easy for the Giants to let the 2014 second-round pick walk after the season.

Jones will be a restricted free agent, so the Giants will be able to retain him on a one-year contract worth just shy of $2 million. The Giants should draft a center in the mid-to-late rounds to compete with Jones next season. Then the Giants would head into 2019 with the option of re-signing Jones or inserting the young center.

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Left guard

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Jack Dempsey | AP Photo

I'm sure many Giants fans will jump ship on this plan after seeing that it includes Pugh. I understand the hesitancy to invest in the injury-prone 27-year-old, but I have a hard time letting the team's best offensive lineman leave. There are enough holes on the line without creating another one.

The big concern with Pugh will be the price tag. But his injuries may work in the Giants' favor, as other teams will likely be equally reticent to shell out big bucks for a player who has missed 10 games (and counting) in the past two seasons.

If Pugh is able to fetch the top of the guard market ($10-12 million per year), the Giants may have no choice but to let him walk. But if he's in that next tier, I think he's worth it. Pugh was having an excellent season at left guard in 2016 before he was slowed by a knee injury. The key for Pugh's contract would be tying hefty bonuses to playing time.

This team needs some homegrown players who understand and value what it means to be a Giant. Keep in mind, Pugh moved from left guard to right tackle without complaint in a contract year. That type of leadership should count for something.

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Right guard

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Bill Kostroun | AP Photo

The Giants landed Fluker last offeason on a one-year, $3 million "prove-it" contract after the 2013 first-round pick flamed out with the Chargers. Fluker was a rare offensive line hit for Reese in recent years, even though former coach Ben McAdoo buried the 6-foot-5, 339-pounder until his hand was forced by injuries.

Fluker has his shortcomings in pass protection, but he made a monster impact in the run game. John Jerry, who has been quietly steady this season, is also under contract for next year to provide competition. Fluker is going to be seeking a longer deal, so something in the neighborhood of what Jerry got last season (three years, $10 million with $3.3 million guaranteed) seems reasonable.

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10 biggest disappointments

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Right tackle

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Brad Mills | USA TODAY Sports

The interior of the line was a piece of cake compared to the challenges that will face the new GM at the tackle spots.

Ereck Flowers progressed from train wreck to serviceable this season at left tackle. That was huge progress for the No. 9 pick in the 2015 draft, but there's no way Flowers can remain this team's left tackle. The Giants schemed around Flowers' (and others') deficiencies in pass protection, which severely limited the offense this season. Flowers may not be any better at right tackle, but that was his projected position by many all along. Guard is another option, but I'd first move him to right tackle to see if that allows him to get back to his roots as a punishing run-blocker.

Let Flowers, Chad Wheeler and a cheap veteran compete for the right tackle job. The loser of the competition will serve as the swing tackle, which will at least prevent Pugh from having to move outside if disaster strikes again.

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Left tackle

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Tom Szczerbowski | Getty Images

This is where the new GM is going to earn his money. It should sure would be nice to have signed Andrew Whitworth last offseason to have this position solidified for the next year or two, but that ship has sailed.

There are no Whitworths set to hit the market this offseason, so the new GM will need to get creative. Nate Solder is the best left tackle set to hit free agency, but he's not a star and there are no signs that he'll leave New England.

The Giants are on track to have the No. 2 pick and in some years that could land a franchise left tackle. But there aren't believed to be any Orlando Paces or Jonathan Odgens in this draft class, plus the Giants will likely target a quarterback with their top pick.

The path to landing a quality left tackle figures to come via trade or a veteran cap casualty. The most obvious trade candidate as of now is Buffalo's Cordy Glenn, who has three years remaining on the five-year, $60 million extension he signed in 2016. Glenn was on the trade block this year, so he should be available in the offseason. Maybe a 2019 mid-round pick and cornerback Eli Apple would be enough for Buffalo to pull the trigger. Glenn won't be the only option, as veterans hit the market every offseason.

The Giants should also use a draft pick (perhaps the one at the top of the second round) to add a tackle to be groomed to take over long-term.

The Giants made a big investment at left tackle when they drafted Flowers in the top 10 three years ago. That was a swing and a miss, so it's time to take another crack at it. They can't just sit back and hope things work out. That's what got them into this mess in the first place.

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Dan Duggan may be reached at dduggan@njadvancemedia.com. Follow him on Twitter @DDuggan21. Find our Giants coverage on Facebook.