Editor's note: This story was published before Derek Carr signed his contract extension worth $125 million over five seasons.

Last year, over the course of a week, I wrote progress reports for three quarterbacks from the Class of 2014. It was reasonable at the time to suggest that none of those three passers -- Blake Bortles, Teddy Bridgewater or Derek Carr -- had separated from the others. If anything, Bortles was getting the most hype after throwing 35 touchdowns during his second NFL season.

A year later, those comparisons seem silly. Bortles continued to be turnover-prone as his mechanics fell apart during his third season, while Bridgewater suffered a catastrophic knee injury and missed the entire year.

In Oakland, meanwhile, Carr took a huge leap forward and was one of the best quarterbacks in the league. While I believed Carr was the best-positioned of those three passers, I was surprised by how effective he performed last season. In addition to leading the Raiders to a 12-3 record in his 15 starts, Carr produced a staggering seven fourth-quarter comebacks, cut his interception rate in half and finished seventh in the NFL in adjusted net yards per attempt. He was a legitimate top-10 passer in 2017.

Now, as Carr approaches what will be a massive contract extension, Raiders fans will wonder whether Carr can take another leap forward into the stratosphere of quarterbacks like Aaron Rodgers and Tom Brady. It's hardly out of the question, given how Carr has continually improved and drastically exceeded expectations over the course of his young career. It's also entirely possible that Carr declines from a banner 2016 campaign, just as Andy Dalton did after his breakout in 2015. Figuring out which is more likely requires a closer look.

The improvements

More than any other passer in the league, Carr is a quarterback of extremes. He's been a different player in each of his three pro seasons, flashing brilliance in one element of his game before regressing toward the mean. The good news? The elements of his game that have showed some consistency peg him as an above-average passer.

In 2014, Carr was incredible in the red zone. He posted a league-best 97.3 QBR inside the opposition's 20-yard line, improving numbers that were below-average over the other 80 yards of the field. The Raiders were subsequently the league's most efficient red zone offense, averaging 5.7 points per trip. Over the ensuing two seasons, however, they've ranked 10th and 11th in red zone scoring efficiency, while Carr has posted a 49.8 QBR on his red zone plays, 27th overall. What looked like a building block of a character trait was more easily explained by the randomness of a small sample.

But randomness has gone Carr's way, too. In 2015, he dropped off dramatically during the second half, falling from 11th in QBR during the first nine weeks to 28th over the final eight weeks. Injuries to star wideout Amari Cooper and key center Rodney Hudson could explain part of that drop off, but it was fair to wonder whether teams had figured something out about Oakland's young quarterback.

Research that I conducted suggested a second-half dip didn't have any sort of predicative value for a quarterback's future, and indeed, Carr improved from his 30th-placed finish in opponent-adjusted QBR back in 2015 to 16th last season. He did drop off some from half-to-half in 2016, falling from 10th in QBR during the first half of the year to 23rd after Week 9, but again, there's no reason to think that will be telling in terms of Carr's future. A broken finger suffered against the Panthers in Week 12 may have also affected Carr's numbers.

Derek Carr threw 25 interceptions in his first two seasons, but just six in 2016. Kyle Terada/USA TODAY Sports

The biggest improvement Carr made between 2015 and 2016 was in avoiding interceptions. Carr more than halved his interception rate, dropping from 2.3 percent to 1.1 percent, good for the fourth-best figure in football, behind only Brady, Dak Prescott and Sam Bradford.

Brady and Bradford each threw shorter passes than the league average. So did Carr, and his presence in that group helps explain why he threw fewer picks. Carr's average pass only traveled 7.3 yards in the air last season, down from 7.7 air yards per pass in 2015. He threw the sixth-shortest average pass in football, which seems odd, given both his skill set and the play of the offensive line in front of him.

Will that interception rate improvement stick? Probably not. Virtually no quarterbacks maintain an interception rate quite that low from year-to-year, even in an era when interceptions are at record lows. From 2002-15, there were just eight instances of a quarterback posting an interception rate of 1.25 percent or less over 300 pass attempts before throwing 300-plus pass attempts again the following year. Just one of those passers -- Brady in 2015 and 2016 -- maintained their pick rate, while the average interception rate for those passers was back up at 2.0 percent.

Part of the explanation is luck. Football Outsiders calculates an adjusted interception rate for quarterbacks by removing interceptions on Hail Mary passes or passes tipped by a receiver before adding would-be interceptions that were dropped by an opposing defender or broken up by a wide receiver. By this measure, Carr threw 12 adjusted interceptions, as opposed to the six picks attached to his name last year, which bumps his interception rate up to 2.1 percent and pushes him to 11th in the league.

The context

The toughest problem with evaluating Carr is also the biggest thing working in his favor: He has about every toy a young quarterback could want. Carr has a bona-fide No. 1 wide receiver in Cooper, who took another step forward in 2016 and doesn't turn 23 until later this month. Cooper is joined by one of the league's best No. 2 wideouts in Michael Crabtree and a high-upside receiving back in Jalen Richard. With the addition of Jared Cook, who finally gives Carr a weapon with soft hands at tight end, Carr has a range of receivers to work with at all levels of the field.

But for all of their potential, Oakland's receivers drop passes too frequently. This was one of the issues expected to improve for Carr last year, but the drops actually got worse. ESPN Stats & Information suggests that 5.1 percent of Carr's passes were dropped in 2015, which was the second-worst rate in the league for regular quarterbacks, topped only by Bradford.

Bradford moved to the Vikings and saw his drop rate plummet to 2.5 percent, helping lead to a career season for the former No. 1 pick. Carson Wentz took over in Philly and got no help from the receivers Bradford left behind, who also posted a 5.1 percent drop rate. As for Carr, well, his receivers managed to drop 5.5 percent of his throws. Only Matthew Stafford, Ryan Fitzpatrick and Colin Kaepernick had worse luck.

The problem in fixing the drops is that there's no lone culprit to replace. Among receivers with 100 targets or more over the past three seasons, each of Oakland's three top wideouts rank among the 40 most drop-prone receivers in football. Crabtree sneaks in at 39th, but Cooper (at 5.5 percent) is 16th, while Seth Roberts's 8.4 percent drop rate is the worst in the league by a comfortable margin (second-placed Eric Ebron came in at 7.7 percent). The only addition the Raiders made at wideout this offseason was in adding Vikings deep threat Cordarrelle Patterson, so Roberts is unlikely to lose many reps as the third wideout. Carr will have to either make better throws or be luckier on the other end of his passes to improve his drop rate in 2017.

Derek Carr benefitted from one of the NFL's best offensive lines in 2016. Jake Roth/USA Today Sports

Carr also has one of the league's best offensive lines protecting him, a unit that stayed healthier in 2016. Oakland's five starters -- Donald Penn, Kelechi Osemele, Rodney Hudson, Gabe Jackson and Austin Howard -- missed a total of just six games last season, five of which came from Howard, the line's weakest link. The Cowboys were the only offensive line that could have made an argument to stand with the Raiders as the league's best last year, and with Dallas losing Ronald Leary and Doug Free this offseason, Mike Tice's unit is the prohibitive favorite to be football's best in 2017.

Although he went down with a fractured fibula in December, Carr spent most of the season living a blissfully defender-free existence. He was sacked just 16 times in 15 games, which is remarkable when you consider that Rams quarterback Jared Goff was taken down 22 times in December alone. Carr was pressured on just 19 percent of his dropbacks, the second-lowest rate in football behind Drew Brees. Teams that sent blitzes were again burned, as Carr posted the third-best QBR in football on non-screens against the blitz, behind only Alex Smith and Rodgers. Carr was eighth in the same category a year ago.

While Carr didn't throw deep quite as frequently as he did in 2015, he remained excellent on deep passes. His 94.2 QBR on passes 16-plus yards downfield was ninth in the league, while his 111.0 passer rating on those throws was good for sixth overall. Again, Carr needs help from his receivers on these passes; Oakland receivers dropped five of his 85 deep throws last year, the second-highest rate in football behind Ryan Tannehill in Miami.

In addition, while it's not captured in the traditional numbers, Carr made hay in terms of generating penalties. Despite missing the season finale, Carr accrued a league-high 19 pass interference penalties against opposing defenders, good for 287 additional yards of offense. Bortles, coincidentally, was the only quarterback to top the latter mark.

The contract

Under his current deal, Carr represents one of the biggest bargains in football. In the fourth and final year of his rookie contract, Carr will take home less than $1.2 million, which is roughly what Tannehill will make per game in 2017. Carr would also hit unrestricted free agency after the season, at which point a team like the Browns or 49ers would presumably pay him a small fortune to take over as their starting quarterback. Of course, Carr will not get there. The Raiders will either sign him to a lucrative contract extension or lock him up for the 2018 season with the franchise tag.

General manager Reggie McKenzie is going to keep his star quarterback around for a long time. The only question is how much it will cost the Raiders, which is hardly an academic debate. McKenzie obviously wants to keep Carr around, but every dollar committed to Carr as part of his extension can't be spent on another player in another contract. There's an opportunity cost in signing players to massive deals, and while the difference between $50 million and $60 million in guarantees might seem mostly irrelevant, that extra $10 million can go to the secondary pass-rusher or cornerback who might eventually push the Raiders over the top.

The dream deal for quarterbacks heading into their second professional contracts is the five-year, $123.0-million contract the Colts gave Andrew Luck before the 2016 season. Luck's deal guaranteed $44 million at signing, but the critical number is the $75 million Luck will take home over the first three years of his new contract. That's a hefty bump on the $67.2 million afforded Cam Newton as part of the five-year, $103.8-million extension the Panthers quarterback signed before his MVP season in 2015.

Carr's agents likely will throw Luck out there as a comparable, given that each quarterback would be signing a deal with one year to go before hitting unrestricted free agency. The problem isn't talent but instead economics. When the Colts signed Luck, he was entering the fifth-year option of his rookie deal, which guaranteed the former first overall pick $16.2 million. As a second-round pick, Carr has no fifth-year option, with the final year of his deal paying out just that $1.2 million figure.

Derek Carr should become one of the highest-paid quarterbacks in football this offseason. Kirby Lee/USA TODAY Sports

The $15 million gap between those two numbers is hardly insignificant. If the Colts had been unable to sign Luck, they could have feasibly franchised him twice and paid him about $63 million for three years of service. If the Raiders can't re-sign Carr, they can franchise their quarterback twice and pay him something around $51.7 million over the next three seasons. (The difference between the two deals is less than $15 million because of salary cap inflation between 2016 and 2017.)

The more plausible comparable for Carr is Russell Wilson. Like Carr, Wilson wasn't a first-round pick, so the Seahawks didn't have a fifth-year option after Wilson broke out. He was owed a $1.5 million base salary before the final year of his rookie deal in 2015, which the Seahawks unsurprisingly supplemented with a four-year, $87.6 million extension. Wilson's deal was worth $56.6 million over its first three seasons, more than the $45.4 million the Seahawks would have needed to give Wilson if they had decided to play out his rookie contract and franchise the QB twice.

A reasonable baseline for a Carr deal would be for the Raiders to pay out a 20 percent premium over the two-franchise-tag baseline that I mentioned as part of a five-year extension. In that case, the Raiders would be handing Carr just over $62 million during the first three years of his new pact. McKenzie prefers to eschew large up-front signing bonuses -- the largest signing bonus for a non-rookie deal on Oakland's roster is the $1.4 million given to Austin Howard -- so Carr should expect to receive huge roster bonuses during the first two years of his contract.

What can Carr expect the total value of the contract to be? With quarterbacks, of course, the rules tend to go out the window. Strictly by looking at comparables, it would make sense to see Carr end up with a five-year extension worth somewhere in the $115 million range, which is good for an average of $23 million per year. The pressure to top Luck's deal and make Carr the highest-paid quarterback in the league, though, may be enough to give the Fresno State grad five years and $123 million, which would top the $122.97 million Luck picked up from the Colts.

The verdict

There's a chance we've already seen Carr's best season, at least for a while. Career paths aren't linear, and even quarterbacks who have long careers can have an early peak before settling in as above-average passers. In terms of adjusted net yards per attempt (ANY/A), Ben Roethlisberger averaged 7.5 ANY/A during 2005, his second season, but then failed to top that mark for a decade before beating it in 2014. Carson Palmer was an MVP candidate during his second season on the field (and his third in the league) before tearing his ACL in the playoffs; he set his ANY/A mark there in 2006 and only surpassed it in 2015, two organizations later. Quarterbacks like Mark Brunell and Philip Rivers had their best seasons during their third and fourth campaigns, respectively, as starters.

On a micro level, outside of his interception rate regressing toward the mean, there are plenty of reasons to think Carr will continue to be an above-average quarterback. The one other element that he'll find difficult to keep around, though, are those fourth-quarter comebacks. In 2015, Carr tied for the league lead with four such wins with Jay Cutler, Peyton Manning and Matt Ryan. Last year, he increased his total to seven, which would have been tied for the single-season NFL record if it weren't for Stafford posting eight comeback wins for the Lions last year.

It's virtually impossible for Carr to pull that off a second consecutive time. There have been seven instances of passers producing six or more comeback wins in a season before 2016, and the following year, those passers produced a total of 10 fourth-quarter comebacks. Just one quarterback in NFL history, Steve Bartkowski, has produced as many as five fourth-quarter comeback wins in consecutive seasons. The odds are against Carr.

With that in mind, it's difficult to see the Raiders repeating their 12-4 performance from a year ago. They only outscored their opponents by 31 points, producing a Pythagorean Expectation of 8.7 wins; Jack Del Rio's team made it to 12 wins by going a remarkable 8-1 in games decided by seven points or fewer. They were 5-5 in the same games the previous year. It's possible that the Raiders have learned "how to win," but history tells us teams that are that good in close games almost always struggle to repeat the feat. Carr might be just as good in 2017 as he was in 2016, but chances are that he -- and the Raiders -- won't reap the same benefits from his level of play.