Are the markets for Bryce Harper and Manny Machado finally beginning to take shape?

According to a source, there is momentum building toward Harper's return to Washington, while the Phillies -- who are set to meet with Harper this week in Las Vegas -- appear to be turning up their pursuit of Machado.

"It's heating up," the source said.

Each of these landing spots would be completely logical, though they're far from certain at this point. Here's a look at why these two potential moves make sense for both the players and the clubs:

The logic behind Harper returning to Washington

• The Nationals have Juan Soto, Adam Eaton and Victor Robles lined up to play the three outfield spots, though the loss of Harper would leave a gaping hole in Washington's offense. Bringing back the face of the franchise would be a popular move with the fan base, keeping the best position player in franchise history in a Nats uniform.

• Harper's market consists of the Nationals, Phillies, White Sox and possibly the Dodgers. The Phils are clearly itching to spend money, but the White Sox -- despite their pursuit of both Harper and Machado -- might not be willing to write a check large enough to land one of the market's two biggest fish. So, in the end, this might just be Philly vs. D.C.

• The Nationals have already made Harper an opening offer, reported to be 10 years and $300 million. Boosting that offer by $25 million to 30 million isn't a stretch, and Harper and his agent, Scott Boras, are said to be seeking the biggest deal in history, which belongs to Giancarlo Stanton (13 years, $325 million).

• One major question is whether Harper and Boras are intent on getting the biggest deal in history in terms of total dollars, average annual salary or simply the biggest free-agent deal of all-time. The latter belongs to Alex Rodriguez, who signed a 10-year, $275 million deal with the Yankees in 2007 after opting out of the final three seasons of the 10-year, $252 million pact he signed with the Rangers before the '01 season. Bottom line: Harper might get a deal somewhere between A-Rod's and Stanton's, and Boras could still claim the "record" for largest free-agent contract ever.

• Harper's deal will likely include an opt-out clause that would allow the former National League MVP Award winner to hit the free-agent market again at the age of 29 or 30, so whatever contract he signs, it will be interesting to see what the dollars look like before any opt-out clause presents itself.

• Another thing to consider: Boras has shown a willingness to get creative with contracts. The deals signed by Yusei Kikuchi and Zach Britton this winter have included opt-out clauses as well as options for their teams to guarantee more money and years on the back end of the contract. Boras could try something similar with Harper and the Nationals, a team with which the agent has a superb working relationship. Washington deferred a substantial amount of money for both Max Scherzer and Stephen Strasburg -- two star players also repped by Boras -- to help get deals done.

The logic behind Machado to Philly

• From the moment Phillies owner John Middleton talked about spending "stupid" money earlier in the offseason, it has been widely assumed that Philadelphia would do whatever was necessary to land either Machado or Harper. Sources have said the Phils were more interested in the infielder, though a return to Washington for Harper would make Machado the obvious No. 1 target.

• The Yankees, Phillies and White Sox have been the three teams pursuing Machado, who wants to play shortstop but appears amendable to the idea of moving back to third base. Philly has Jean Segura penciled in at shortstop and Maikel Franco at third. If the Phils sign Machado, Segura could play second (where he has played in the past), making Cesar Hernandez a trade candidate. Or they could deal Franco, opening up third for Machado with Hernandez staying at second base. And behind all of them, they have Scott Kingery , who can play second, short or third. No matter what happens, they have roster flexibility should they make this move.

• There's also this: If Harper returns to the Nationals, the Phillies' competition in the NL East would be even steeper, making the need for the Phils to make a big move more pressing. The Mets and Braves have gotten significantly better this offseason, and a Harper-Nationals reunion would keep Washington firmly in the mix for a division title.

• The Yankees have been widely viewed as Machado's preference, but New York has reportedly been unwilling to go as high as $300 million or as long as 10 years. If the Yanks hold firm to their limits -- and given their restraint in the Patrick Corbin sweepstakes, there's no reason not to think they will -- then Machado might have to decide whether he is willing to take fewer years and/or dollars to play in the Bronx. Historically, the team offering the bigger deal tends to get the guy.

• Next year's free-agent class also includes a pair of All-Star third basemen ( Nolan Arenado and Anthony Rendon ), so the Yankees could opt to wait a year and pursue one of them instead of Machado. New York will be one year closer to shedding Jacoby Ellsbury 's onerous contract at that time, while Carsten Sabathia ($8 million) and Brett Gardner ($7.5 million) will also be coming off the books.

• Even if you doubt that the Yankees are serious about Troy Tulowitzki as their full-time shortstop in 2019 -- or simply want to hedge due to his history of injuries -- there are plenty of lower-cost middle-infield options on the market they could explore if they want to add some depth in the absence of Didi Gregorius, who will miss the first half of the season recovering from Tommy John surgery. For example, they could bring in someone like Freddy Galvis , who could back up Tulo and become more of a jack-of-all-trades when Gregorius returns.