Who might bid on Harper after 2018?

Having already agreed to a contract for 2018, Bryce Harper can focus exclusively on baseball for the next 17 months or so. Then the real fun begins.
Harper will earn $21.65 million next season, his final year before he heads to free agency. That's the highest salary in history for an arbitration-eligible player, which is not shocking given Harper's résumé and the fact that he's off to another stellar start in 2017.
The two sides discussed a two-year deal when they were negotiating this past offseason, but with Harper coming off a mediocre season, the Nationals and agent Scott Boras decided to settle on a $13.625 million deal for this season only. After Harper's hot start, talks resumed and a deal was struck, removing any possibility of a hostile negotiation next offseason.
"I wouldn't read into it a whole lot," one industry source with knowledge of the situation said. "There was no talk of anything beyond that -- and there's not going to be."
One general manager found the mid-May timing of the deal "curious," wondering, "Why now?
"Is it to know cost certainty for next season for budgetary reasons? Is it to get one element of the framework for a possible extension out of the way?" the GM said. "Is it so that if they want to trade him, everybody knows what he costs? Any -- or all -- are possible."
Here's what we know: Harper will headline a star-studded free-agent class after the 2018 season, one that also includes Manny Machado, Josh Donaldson and Dallas Keuchel.
Unlike most big-ticket free agents, Harper will be only 26 when he hits free agency, still a year away from the "prime" years of his career. The numbers that will be floated figure to be astronomical, so which teams will be able to make a legitimate bid for the former -- and future -- MVP Award winner?
"It's going to be a pretty shallow pool that can play," the GM said.
Or will it be deeper than most experts predict?
"There may appear to be only a few suitors, but who knows?" the industry source said. "None of us expected Arizona to sign [Zack] Greinke, either. … I never say never anymore. You never know who is going to kick the tires."
Here's an early look at the possible suitors for Harper when he becomes a free agent after the 2018 season. We've broken them down into three categories: Likeliest suitors, in the mix and dark horses.
Likeliest suitors
Yankees
This is the most obvious fit. From Harper's much-publicized fandom as a kid to the Yankees' history of making sizable free-agent signings, the Yanks will be the odds-on favorites to sign the outfielder.
The only position players under contract with the Yankees beyond 2018 are Jacoby Ellsbury (signed through '20) and Starlin Castro ('19). Assuming Aaron Judge is occupying one of the other two outfield spots, there's still room for Harper to ply his trade in a ballpark that is friendly to left-handed sluggers. The Yanks have a total of $74 million committed to four players in 2019, though that number drops to $52 million if Masahiro Tanaka opts out after this season.
The team's long-stated goal of getting under the luxury tax threshold could finally become reality in 2018, which would reset the Yankees' tax rate and make a huge nine-figure contract a little more palatable for the Yanks, who have several young players (Judge, Gary Sánchez, Greg Bird, Gleyber Torres, etc.) under control at team-friendly costs for several years.
Nationals
It's a foregone conclusion Harper will test the free-agent market, but that doesn't mean he's necessarily leaving Washington. The Nationals have money locked up for Max Scherzer and Stephen Strasburg through 2021 and '23, respectively, while Ryan Zimmerman and Adam Eaton are signed through '19 with team options for '20.
But Jayson Werth's contract ends after this season, while Daniel Murphy's deal is up after 2018. Oh, and the Nats will have $21 million coming off the books with Harper, which can be put right back into a new deal for their best player.
Washington has stepped up with huge deals for Scherzer, Strasburg and Werth -- all of whom are Boras clients -- so it wouldn't be difficult to imagine the Nationals coming up with whatever they need to in order to keep the face of the franchise in D.C.
Rangers
Texas has Shin-Soo Choo, Elvis Andrus and Rougned Odor locked up for roughly $45 million in both 2019 and '20, but with Yu Darvish, Carlos Gómez and Andrew Cashner coming off the books after '17 and Adrián Beltré's contract expiring after '18, the Rangers will have plenty of money to spend. Texas has done plenty of deals with Boras -- who reps Choo, Beltre, Andrus and Gomez -- so it wouldn't be surprising if Jon Daniels checks in on Harper after 2018.
In the mix
Red Sox
The Red Sox have a lot of money committed beyond 2018, with $97 million owed to five players in '19: David Price, Rick Porcello, Pablo Sandoval, Dustin Pedroia and Rusney Castillo, a figure that jumps to $110 million with Chris Sale's '19 option.
Of course, the team's young outfield will still be under control when Harper becomes a free agent, as Jackie Bradley Jr. will be in his final year of arbitration, Mookie Betts in his second year of arbitration and Andrew Benintendi still a year away from his first year of arbitration eligibility. Barring something unforeseen, the outfield wouldn't seem to be Boston's biggest area of need.
Giants
San Francisco has Buster Posey, Brandon Crawford and Brandon Belt signed through 2021, but none of the Giants' outfielders are signed beyond '18, leaving plenty of room for Harper. Nobody has peppered the bay with baseballs with regularity since Barry Bonds; imagine the damage Harper could do taking aim with his big lefty swing at AT&T Park 81 times per year.
Cubs
The Cubs have shown a willingness to spend, but this seems like a long shot. With Jason Heyward signed for big bucks through 2023, Jon Lester inked through '20, and most of their talented young core headed for huge raises in arbitration -- or extensions -- it seems like Chicago's payroll will already be stretched to the limit. The fact that the Cubs' top prospects -- Eloy Jimenez and Ian Happ -- can fill holes in the outfield makes it even more unlikely that Harper winds up calling Wrigley Field home.
Dark horses 
Phillies
Harper loves hitting at Citizens Bank Park, which could make for an enticing landing spot for the slugger. The Phillies have a young club that will be making very little money -- Odúbel Herrera is the only player on the roster signed to a guaranteed deal beyond this season -- while the bulk of their core won't even be eligible for arbitration for another two years. This could be the team to watch outside of the usual suspects.
Angels
The idea of pairing Harper in the same outfield as Mike Trout is intoxicating, but with no pitchers signed long-term and position players Trout, Albert Pujols, Andrelton Simmons and Kole Calhoun all under team control through at least 2020, the Angels figure to spend on pitching rather than making a serious bid for Harper. But they've made surprising free-agent bids in the past, so they shouldn't be discounted.