First, the obvious: Marlins slugger Giancarlo Stanton has legitimate designs on 60 or more home runs this season, and his second-half surge has lifted Miami into wild-card contention. As such, the Marlins -- even though Stanton has already passed through waivers -- aren't going to trade him during the season. However, once the new ownership group publicly fronted by Derek Jeter takes the reins, an offseason trade of Stanton and his mega-contract is a distinct possibility.
As for who would be interested in adding Stanton to the fold, it requires a mix of need, payroll flexibility and risk tolerance (Stanton had an opt-out of his backloaded $325 million deal after the 2020 season, which means his club assumes all of the risk). On that front, Bob Nightengale of USA Today has some tantalizing specifics. He writes:
The San Francisco Giants recently called, and privately informed the Miami Marlins of their interest.
They all have one thing in mind.
They want Miami Marlins slugger Giancarlo Stanton, and while it's not realistic now, it could be by the start of the 2018 season.
Nightengale's piece has much more on the Stanton situation, so give it a read.
As for the four teams he names -- the Giants, Cardinals, Rangers, and Phillies -- they all make sense. That's especially the case with the Phillies, who are working to emerge from a deep rebuild and have negligible long-term salary obligations. The Giants, though, are certainly pining for a reboot after their disappointing 2017 season and would love to resume contending around that core of Buster Posey, Madison Bumgarner and company. The Cardinals have plenty of outfield depth, but they badly need a true middle-of-the-order hitter to keep up with the Cubs and Brewers, who both figure to contend for years to come.
As for Stanton, he has a full no-trade clause, but those are typically more about leverage than anything else. If a team wants Stanton badly enough, then it will persuade him to waive that clause (by guaranteeing his 2028 option, for instance). The contract, meantime, is a huge consideration. The Marlins will surely have to kick in cash, but it's massive obligation no matter what. He's still owed more than $300 million on the deal, and as noted above his opt-out after the 2020 season means that the team takes on the potential downside (i.e., he's probably not going to opt out if he's no longer worth the money he's still owed).
All that said, Stanton, with his massive resurgence in 2017, has established himself as one of the top offensive forces in the game today. Such things don't come cheap. For a team with near-to mid-term designs on the World Series, he'll be appealing. That's assuming, of course, that Jeter and company would want to trade their most valuable contributor and their most visible star.
Developing, people. Very developing.