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Detroit Lions fans should be bracing themselves for yet another potential rebuild.

Though there certainly may be room for optimism following an 11-5 season in 2014 and a playoff appearance in the first year of head coach Jim Caldwell's reign, the success he had may not be sustainable thanks to the poor job done by general manager Martin Mayhew in recent years.

Under Mayhew, who ascended to the role of GM in 2009 after the firing of Matt Millen, the Lions have gone 40-56 and have only been over .500 twice in his six years leading the franchise.

Although he was given a long leash following the depths to which the franchise had fallen under his predecessor (and rightfully so), the Lions are now on the second rebuild of his tenure. That means he is officially out of any benefit of the doubt.

He's been terrible.

Mayhew's best moves as a talent evaluator have been the no-brainers.

The Lions had been quarterback deficient for the better part of…well, forever, when Mayhew took over. Into his lap dropped Matthew Stafford, who may have been the most physically talented sure thing at the position since Peyton Manning.

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Fast forward a year to 2010, and the Lions could have drafted either Ndamukong Suh or Gerald McCoy. Either one would've been a fantastic pick for Detroit, and both have been among the best defenders in the league for their entire respective careers.

Even defensive end Ezekiel Ansah, drafted in 2013 at No. 5 overall, was an easy choice for a team that needed a pass-rusher and valued them highly thanks to then-head coach Jim Schwartz' cautious defensive scheme.

In reality, the only clear impact player the Lions have drafted and still have heading into 2015 who they likely might not have acquired without Mayhew is linebacker DeAndre Levy, who was a third-round pick in 2009 and has taken years to pan out before emerging as one of the league's better linebackers as of late.

In terms of drafting, a public poll may have done better than Mayhew, and it certainly couldn't have done much worse.

Mayhew's 2010 and 2011 Drafts Year Round Player Position Where Are They Now? 2010 1 Ndamukong Suh DT Signed with Miami Dolphins in 2015 2010 1 Jahvid Best RB Out of the league due to injury history well-known prior to draft 2010 3 Amari Spievey CB Moved to safety, eventually cut, out of league 2010 4 Jason Fox OT Re-signed with Miami Dolphins in 2015 2010 7 Willie Young DE Promising young player, now with Chicago Bears 2010 7 Tim Toone WR "Mr. Irrelevant"...only lasted a few years on Detroit's practice squad, out of League 2011 1 Nick Fairley DT Signed with St. Louis Rams in 2015 2011 2 Titus Young WR Out of league with character issues well-known prior to draft 2011 2 Mikel Leshoure RB Out of league 2011 5 Doug Hogue LB Out of league 2011 7 Johnny Culbreath OT Out of league

In all, the Lions have a whopping zero players on the team heading into next year that they acquired in the 2010 and 2011 drafts, causing even Mayhew to concede it was a terrible effort, via Josh Katzenstein of The Detroit News:

I think '11 wasn't a good draft for us. I didn't do a good job in '11. I think I was overly aggressive. I learned a lot from that, and our drafts have improved since then. … I'm just going to leave it at that. You can interpret it how you want to interpret it.

Mayhew and team president Tom Lewand have mismanaged the team to an incredible degree. Some of this, of course, is not their fault. The timing of the Lions' Millen-induced rock bottom coincided perfectly with the tipping point of escalating rookie salaries, and they got into all sorts of salary-cap problems due to the cap hits of Stafford, Suh and wide receiver Calvin Johnson.

Add to that the flat nature of the salary cap over the past couple of years before recent skyrocketing increases over the past year and expected into the future, and it's pretty clear the Lions have been a victim of circumstance as well.

But it's no excuse.

Both Mayhew and Lewand are out of excuses.

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The team did itself no favors with its cap situation, consistently putting off tough decisions by extending players like Suh until cap judgment day hit like a ton of bricks. Worse yet, those extensions consistently freed up cap money for literally no benefit to the team, as Detroit rarely used that money wisely.

It was Suh's contract extensions in 2012 and 2013 that pushed his cap hit so high in 2014 and made it virtually impossible to re-sign him (or franchise him) in 2015. The Lions turned that gold into lead by using a great deal of it to keep players like offensive tackle Jeff Backus around, as well as to acquire players no longer in Detroit like running back Reggie Bush, cornerback Chris Houston and kicker David Akers.

Perhaps that is cherry-picking a bit. Some of that money was also used to extend players like Levy and to acquire more valuable players like safety Glover Quin and linebacker Stephen Tulloch. But overall, what have the Lions really accomplished?

The extensions were meant to keep a core together, but that core hasn't done a darn thing.

At the same time, knowing that re-signing Suh would be a mathematical uncertainty (if not improbability), the Lions chose to decline picking up an option on defensive tackle Nick Fairley's contract in 2014.

This, along with the age of C.J. Mosley, left the Lions without any potential starting defensive tackles in 2015. In turn, that situation led to the costly trade for 31-year-old Haloti Ngata. As I explain here, that move cost the Lions not only draft picks but also a significant amount of the cap space freed up by Suh's departure.

To take this all one step further, it could be argued the Lions' plans over the past few seasons set up a choice between Suh and Johnson. Johnson, owed $12.5 million in 2015 and with massive dollar amounts between now and 2020, is being paid like the Lions' franchise cornerstone.

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However, it is Suh (not Johnson) who has consistently been the best and most impactful player for the Lions in recent seasons, and it is Suh (not Johnson) who is likely to produce more over the next half-decade.

Johnson, at 29, has reached the beginning of a likely decline at a position where (on average) receivers begin to drop in production between 29 and 31. Numerous studies have shown this, but this chart at ESPN gives a good visual aid. Suh, at 28, with less injury history and at a position with considerably more longevity, would've been the better bet over the next five to six years.

Instead, the Lions played hardball with the best defensive player in the league not named J.J. Watt and got burned.

One could argue it was Suh's attitude and temperament that forced the Lions' hand in this regard, but a culture of enabling both from former coaches and the franchise did nothing to quell Suh's penchant for toeing the NFL's lines.

His departure has the potential to be a franchise-altering disaster.

The only real upside of the 2015 offseason so far is that the Lions will likely receive significant compensatory draft pick compensation next offseason thanks to the losses of Suh and Fairley. Yet those mid-round picks mean little when used by a general manager who hasn't hit on a single late-round pick still with the team other than punter Sam Martin.

All of this means the success or failure of Caldwell and his staff matters very little to the Lions' future, because the general manager deserves to be clearly on the hot seat. If Mayhew ends up out the door with a poor (or mediocre, or even static) season in 2015, a new general manager could end up wanting to make his own hire.

Owner Martha Ford, having recently taken over for her late husband, has high expectations, as laid out recently by Lewand, via Dave Birkett of the Detroit Free Press:

There was no ambiguity about the excellence (she expects), starting with winning the NFC North and then moving on to considerable playoff success, including a Super Bowl. So it is very clear that the main measuring stick is success on the field, more so than it is any business metric.

The Lions have never won the NFC North. Their last divisional win was in the old NFC Central in 1993. (Tight end Eric Ebron had just been born.) Their last playoff win was in 1991. (Stafford was likely potty training around that time.)

They haven't had anything resembling "considerable playoff success" since the 1950s and have never won a Super Bowl. Their last championship was in the pre-merger era in 1957—eight years before Mayhew was born.

Low expectations have been a hallmark of the franchise for far too long.

Lions fans are hoping that fact of life changes sooner rather than later, but Mayhew has failed to meet even the lowest of expectations for the better part of his tenure.

To succeed in 2015 and turn Mayhew's stars around—he is, notably, only 49 years old—the Lions need to hope in the continued maturation the of 27-year-old Stafford, who is entering the prime of his career. He took a huge leap under Caldwell and offensive coordinator Joe Lombardi in 2014 and will need to do so again to carry the Lions next season.

The Lions must also hope the rest of 2014's No. 3 scoring defense picks up the slack with the departures of Fairley and (especially) Suh. With even an average defense in 2015, the Lions are likely to slide back into the doldrums of the conference considering the always-tough nature of the NFC North.

Finally, the Lions need to hit not only a home run, but a couple of home runs in the upcoming draft. It won't be easy drafting 23rd overall and without a couple of their original picks, but it needs to happen. Another year of waiting for potential and low expectations could—and very well should—signal the end of Mayhew's career with the Lions and a total shift in the direction of the franchise.

The Lions have been one of the biggest laughing stocks in the league for almost their entire history. 2014 may have begun to turn the tide, and building on that success is both possible and crucial. If they don't, however, it's time to find people who can consistently meet the expectations Mayhew simply hasn't.

He never has, and if 2015 is a failure, it's likely he never will.

Michael Schottey is an award-winning NFL National Lead Writer for Bleacher Report and a writer for Football Insiders. Follow him on Twitter.