Ranking this year's free agents that have the best chance to pull a J.D. Martinez

The free agent class isn't as cut and dried as we like to think it is. We imagine it's like going to the grocery store -- "ooh, a Lorenzo Cain for $80 million? I could use one of those." Instead, it often works out closer to the claw machine at the front of the store. Teams put the money in and hope that they wind up with the grand prize. 
Last year, J.D. Martinez was the top-shelf prize. He slugged home runs. He bashed baseballs all around the park. He nearly won the Triple Crown! He was everything the Red Sox could have dreamed for en route to a World Series title. 
So, who will be this year's Martinez -- a free agent supernova who can lead his team to glory? Let's rank them using this meter, ranging from "Just Don't Care" for a free agent slump to "Just Dingers!" for a new baseball star.
Let's break them down:
Bryce Harper

This is the year people have been thinking about ever since Harper reached the Major Leagues. What happens when a genetic freak with a swing that's like a hammer from the gods reaches free agency in time for his age-26 season? I mean, if he wanted to sign a 20-year contract, there would have to be at least one team that would take the risk, right? 
While Harper has all the talent in the world and has a maturing eye at the plate, he mixes blistering hot streaks with slumps that resemble lemmings tumbling off a cliff. That volatility means there is just too much bust in his boom to be considered a sure thing.
Verdict: 

Manny Machado

With Machado trapped on the sinking SS Orioles for most of the year, and with a cold start to his Dodgers tenure, you may have thought that the infielder's season was a disappointment. But then you actually look his numbers -- .297 AVG, 37 HR and 14 SBs -- and you realize that's one heck of a remarkable season for a shortstop. Remove what appears to be a mirage in 2017, and it's almost a guarantee of an MVP-caliber season.
Whoever gets Machado is going to have more happy days than sad ones.
VERDICT: 

Patrick Corbin

Mix one part falling walk rate with one part rising strikeout rate, add in a dash of a dynamite slider and you get Corbin. If he's not a household name yet, he's going to be with teams like the Yankees rumored to be backing up the Brinks truck to his house this offseason. After all, only five pitchers threw 200 innings or more (Corbin threw exactly 200) while striking out 10 or more hitters per nine innings last year.
In addition to Corbin there was Justin Verlander, Max Scherzer, Jacob deGrom and Gerrit Cole. That's basically a list of Cy Young winners, and 2019 could be Corbin's season. 
VERDICT:

Josh Donaldson

From 2015-2017, the Bringer of Rain posted a .946 OPS and averaged 37 home runs a year while playing a stellar third base. Injuries sapped him of playing time and skill most of last year, but in 60 plate appearances at the end of the year with the Indians, he looked like the player of old.
While he is expected to still play the infield, perhaps a move to DH will convert him into the full J.D. Martinez. The rest would keep him healthy and the home runs would return. Considering that even last year's disappointing "lost" year still resulted in an above-average hitting line, I'd bet on him returning to form.
Verdict: 

Nelson Cruz

Perhaps the most similar player to Martinez. Cruz is a bona fide home run crusher, who has averaged 41 dingers every year since 2014. His 203 homers in that time lead the Majors -- ahead of homer-hitting freaks like Giancarlo Stanton, Edwin Encarnacion and Khris Davis. He may even set new career highs because he could end up in a much friendlier stadium than Safeco Field.
Of course, Cruz is 38 and posted his lowest OPS since he was with the Rangers, so there's reason to be worried.
Verdict: