As evidenced by the ongoing job hunts of both Bryce Harper and Manny Machado, the biggest transactions of the Major League Baseball offseason have yet to come.

Still, there have already been a few that make us go, "Gee, I don't know about this..."

We've taken a look at six early moves with significant bust potential. One is a blockbuster trade that's loaded with risk. Another is a monster extension for a declining player. The other five are surprisingly lucrative free-agent deals for players who are less than sure things.

We'll start with the trade.

The Robinson Cano/Edwin Diaz Trade for the Mets

At the least, the New York Mets' blockbuster trade for Robinson Cano and Edwin Diaz is defensible.

It didn't cost them Andres Gimenez or Peter Alonso. And due to a swap of bad contracts and a $20 million payment from the Seattle Mariners, the Mets are only adding $64 million in guaranteed money. In return, they're getting an eight-time All-Star second baseman and an All-Star closer.

And yet it's hard to downplay the risk of adding Cano alone. Though his bat still plays, he's a 36-year-old whose recent 80-game suspension for performance-enhancing drugs only fuels questions about how much he has left in the tank.

Officially, the Mets are on the hook to pay $100 million of the $120 million owed to Cano through 2023. And while Diaz is cheap now, the 24-year-old might start pulling in eight figures a year via arbitration in 2020.

The Mets won't complain if they win big in the immediate future. To that end, new general manager Brodie Van Wagenen is confident enough to tell reporters: "Internally, we would argue that we're the favorites in the [National League East] right now."

But though the Mets have improved a roster—with not just Cano and Diaz but also Wilson Ramos and Jeurys Familia—that lost 85 games in 2018, they haven't exploited a power vacuum in the NL East. The Atlanta Braves, Washington Nationals and Philadelphia Phillies all figure to be competitive in 2019 and beyond.

If the Mets miss the window they're aiming for, the Cano/Diaz trade could come back to haunt them.

Clayton Kershaw's 3-Year, $93 Million Extension with the Dodgers

There would have been a ton of intrigue if Clayton Kershaw had become a free agent, but he and the Los Angeles Dodgers nixed that by agreeing to a three-year, $93 million contract in early November.

Kershaw was already owed $65 million in 2019 and 2020 under his existing contract. The question was whether he would opt out to seek greater riches on the open market. The Dodgers arguably should feel lucky that it only took $28 million to convince him otherwise. After all, Kershaw is a three-time Cy Young Award winner with the best adjusted ERA+ in history.

However, it's no secret that he's quickly slipping from the ranks of MLB's best pitchers.

The 30-year-old is afflicted with diminishing fastball velocity, which is contributing to the death of his strikeout rate and a problem with home runs. And due to an array of back problems, he's made over 30 starts in only one of the last five seasons.

It never seemed particularly likely that the Dodgers would challenge Kershaw to opt out and allow him to drift away to another team. But if they had, they would have freed up $65 million to invest in either his replacement or upgrades for the rest of their roster.

Over the next three years, they may come to regret not doing precisely that.

Josh Donaldson's 1-Year, $23 Million Contract with the Braves

Back in October, MLB.com's Mark Bowman calculated that the Atlanta Braves had as much as $60 million to invest in the offseason market.

If true, well, more than a third of that went to Josh Donaldson's one-year, $23 million contract. 

This is far from unreasonable. It's only one year, and the money is going to a guy who accumulated more wins above replacement between 2013 and 2017 than every hitter except Mike Trout, according to Baseball Reference. Should the 33-year-old turn back the clock, he'll be a $23 million steal.

Donaldson's age, however, is one reason to be skeptical. There are also red flags planted in a bat that averaged a .901 OPS and 33 home runs in the aforementioned five-year span. His strikeouts are trending up, and his power output suffered a steep decline in 2018.

To boot, calf injuries have limited Donaldson to a total of 165 games since 2017. This raised questions about whether he should stick in the American League, where he could occasionally take a load off at designated hitter. In Atlanta, the Braves will need him at third base on an everyday basis.

Ultimately, $23 million for Donaldson is a deal that likely has no in-between. It's either going to be a huge success or a massive letdown.

Joe Kelly's 3-Year, $25 Million Contract with the Dodgers

If you can't beat him, sign him.

The Dodgers presumably had more in mind when they agreed to a three-year, $25 million contract with Joe Kelly, but what he did to them in the World Series is still fresh. The right-hander pitched in all five games for the Boston Red Sox and struck out 10 with no walks or runs allowed in six innings.

Kelly's World Series performance is a tantalizing tease of his potential. He is, after all, a reliever with a 98.1 mph average fastball and three viable secondary offerings: a curveball, slider and changeup.

Trouble is, fascination with Kelly's stuff typically goes hand in hand with frustration over his results. 

The 30-year-old has been better as a reliever (3.29 ERA) than he was as a starter (4.13 ERA), but his career performance can be described charitably as "all over the place." He's far from an elite bat-misser despite his electric stuff, and he serves up too many free passes.

So it went for the majority of 2018. Kelly finished the regular season with a modest ERA (4.39) and strikeout-to-walk ratio (2.1). Though he and his peers ultimately came through, he was a big reason why many had doubts about Boston's bullpen going into the postseason.

The Dodgers are effectively banking on Kelly picking up where he left off in October. It's at least as likely that he'll go back to being, well, Joe Kelly.

Lance Lynn's 3-Year, $30 Million Contract with the Rangers

Lance Lynn's three-year, $30 million contract with the Texas Rangers might be the most eyebrow-raising deal of the winter so far. It's nearly twice what MLB Trade Rumors and Fancred's Jon Heyman projected he'd get.

There's no blaming Lynn for accepting it, of course, and it's even understandable why the Rangers would reach for him. They sorely needed to upgrade a starting rotation that put up a ghastly 5.37 ERA in 2018.

Lynn, 31, is a veteran innings eater who should at least stabilize Texas' rotation. He could do more than that if he carries over what was working for him down the stretch with the Yankees this year. He whiffed 61 and walked only 14 in 54.1 innings.

However, even Lynn's strong finish only did so much to salvage his season.

He put up a 4.77 ERA overall, including a pedestrian 4.14 ERA with New York. Left-handed batters got him to the tune of an .841 OPS. Going forward, right-handed batters might adjust to the subtle change—MLB.com's Mike Petriello covered it well—that fueled Lynn's late-season improvement against them.

So while this deal can certainly be rationalized from both ends, it's still a larger-than-expected contract for a middle-of-the-road pitcher.

Nathan Eovaldi's 4-Year, $68 Million Contract with the Red Sox

The bulk of Nathan Eovaldi's four-year, $68 million contract with the Red Sox might as well be for past services rendered.

The 28-year-old put up a 3.33 ERA in 54 innings for Boston at the end of the regular season. He then went full Bumgarner in October with a 1.61 ERA in 22.1 innings. The last six of those innings came in a downright heroic effort in Game 3 of the World Series.

Much like Kelly's, Eovaldi's postseason dominance might be a springboard to sustained success. After years and years of frustration, he may finally translate his overpowering arsenal into ace-level production.

However, whether Eovaldi can even stay healthy is a question in its own right. He's already had two Tommy John surgeries. And while his frequent 100 mph fastballs are fun to watch, research from Jeff Zimmerman of The Hardball Times suggests that high-velocity pitchers are at greater risk of arm injuries.

There's also the matter of Eovaldi's career track record. He owns a pedestrian 4.16 career ERA. Like Kelly, he serves up a surprising rate of contact for a guy with such great stuff.

In all, this is a deal worthy of both applause and crossed fingers.

Patrick Corbin's 6-Year, $140 Million Contract with the Nationals

It's not a surprise that Patrick Corbin made a ton of money on the open market. What's surprising is that he made this much.

The left-hander's six-year, $140 million pact with the Washington Nationals topped MLBTR's projection by $11 million and Heyman's by a whopping $40 million.

Still, the deal is more reasonable than it might seem. In Corbin, Max Scherzer and Stephen Strasburg, the Nats rotation features perhaps the best front three in MLB. 

All the same, this deal doesn't happen if Corbin, 29, doesn't finish 2018 with a 3.15 ERA and 246 strikeouts in 200 innings. He made a lot of that happen on his own, but he also got a boost from the Arizona Diamondbacks' catching corps, defense and pitcher-friendly home ballpark. The Nats will walk a fine line in replicating those advantages.

Though he's not in the same boat as Eovaldi, Corbin also comes with some injury concern. He has Tommy John surgery in his background.

The Nationals aren't wrong to bet on the addition of Corbin being a wild success. But in a couple of years, they could be wishing they had saved his $140 million for Harper.

Stats courtesy of Baseball Reference and FanGraphs. Contract and payroll data courtesy of Cot's Baseball Contracts.