Hall of Fame coach Bill Parcells has a great line about a coach's relationship to an NFL roster: "If I'm going to be asked to cook the meal, I'd like to be able to pick the groceries." Not every coach gets that luxury, of course, and that desire from Parcells is one reason he parted ways with the New England Patriots despite leading them to a Super Bowl appearance.

Allow me to add an addendum: If you're going to ask someone to cook the meal, don't give them a bag of rotten ingredients.

That's the problem Jim Caldwell faces in Detroit: Management wants him to cook up a winner, but it hasn't given him hardly any of the ingredients.

Jim Caldwell

In fairness: Caldwell chose to be the Lions' head coach, and when he did accept the position before the 2014 season, the cupboards were far better stocked than they are now. And that team did a respectable job, going 11-5 and suffering a controversial loss to Dallas in the NFC wild card Game.

A lot has changed since then. The Lions lost defensive tackles Ndamukong Suh and Nick Fairley in free agency, and released contributing running back Reggie Bush. Those losses would seem to indicate that a regression was due for the defense, and granted, that side of the ball hasn't fared particularly well. But the big surprise this year -- and the one that has proven traumatic for the franchise -- is the trainwreck that's occurred on the offensive line.

Few people saw this coming. The Lions entered 2015 with a middling-to-above average prognosis for its O-line. Instead, it's been a complete mess. Matthew Stafford is throwing under pressure at a career-high rate, and it isn't going well. Although his completion percentage is up for 2014, his adjusted net yards per attempt are the lowest of any season except his rookie year in 2009. He's throwing interceptions at a disastrous rate: 11 through eight games, compared to 12 all last season.

It's lackluster enough that he was benched in a game last month, all while Lions observers fire up the conversation that it's time to dump Stafford as a "franchise" quarterback.

Caldwell was brought in partially because of his track record with quarterbacks. He coached a young Peyton Manning to greatness and was the Baltimore Ravens' offensive coordinator when Joe Flacco's emergence lifted the team to a Super Bowl championship.

Matthew Stafford

In that sense, Caldwell is failing with Detroit in two regards: His team is underperforming, and he's failed to develop the team's starting quarterback.

Again, this is where the offensive line has failed him. Stafford is hardly getting a chance to succeed under center behind an ugly offensive line. Rookie guard Laken Tomlinson has been a poor contributor, and Larry Warford isn't healthy to boost the unit. The Lions have no respectable answer to the right tackle position, and it means Stafford is tasked with doing more than he's capable of.

Again, Caldwell doesn't deserve a pass on how he's groomed Stafford under center. But Detroit's roster is shot full of holes and in need of contributors all over the field. That's why team president Tom Lewand was fired, along with general manager Mayhew: A once-promising roster has collapsed under the weight of mismanagement.

How's this for signs you've done a bad job: None of the Lions' 2010 or 2011 draft picks is still on the team's roster. That's two years of rookie talent flushed away, with nothing in return. It's not just first-round picks Suh and Fairley, either: Ryan Broyles and Titus Young never progressed from second-round picks to contributing receivers, while defensive prospects like Kyle Van Noy and Louis Delmas couldn't prove to be capable starters.

Ndamukong Suh and Nick Fairley

Never mind that the Lions had an underwhelming offseason on the free agent market, losing two of their highest-profile players and failing to add a single impact player. Perhaps no one saw this team starting 1-7, but the Lions were primed for regression. Just looking at the roster, how could they not?

Earlier this season, amid a stalling offense and increasing vitriol, the team fired Joe Lombardi as offensive coordinator. It looked more like a sacrificial offering than a step toward any real progress. Even in her press conference Thursday, Detroit Lions owner Martha Ford said the team wasn't giving up on the season. Sure, maybe they won't, but let's be clear: This season is already lost.

The question now is what becomes of Caldwell. You can't point to the gutted roster and depleted coaching staff and ask him to coach for his job. Some younger players like Tomlinson might show some progress, but any gains in the second half of the season will be incremental. Instead, Ford needs to focus on finding a GM that knows how to work the draft.

Ultimately, a decision will have to be made on Caldwell. It's hard to envision any head coach surviving a two- or three-win season in his second year, and while coming off a playoff appearance -- even when the situation is as grim as the one Caldwell's been handed. His quarterback pedigree could prove useful in developing a rookie quarterback from next summer's class, a move Detroit seems increasingly likely to make. But it's just as likely he'll be canned this winter, and sent packing to find an attractive OC position elsewhere.

That's the nature of the business. But Caldwell's failures this season shouldn't affect his reputation too much. You can't build a winning team when you consistently fail in the NFL draft. Everyone knows that -- even Mayhew himself acknowledged that earlier in the season.

Nor can you win games with a losing roster. Caldwell's no magician -- he's only a football coach.

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