NASHVILLE, Tenn. -- With David Price and Zack Greinke having signed huge deals, outfielder Jason Heyward is the obvious best player left on the market in this free-agent class. It's possible the fact that he hasn't signed yet is holding up the signings of other big-name outfielders Justin Upton, Yoenis Cespedes and Alex Gordon.

We haven't been lacking for reported Heyward suitors, either. The latest buzz from CBS Sports MLB Insider Jon Heyman says the Giants, Cubs, Cardinals and Angels are the teams involved in the bidding. He also mentions the inclusion of a fifth team that isn't yet known.

Yes, the "mystery team," an annual Winter Meetings tradition. We've seen the mystery team win. Think of Cliff Lee signing with the Phillies or Albert Pujols to the Angels. It wasn't at the Winter Meetings, but Prince Fielder to the Tigers came from out of nowhere.

So while this is purely speculative, these are some teams that might be the so-called mystery team that sweeps Heyward off his feet.

Might Jason Heyward be our next free agent to pick a 'myster team?'
Might Jason Heyward be our next free agent to pick a 'mystery team?' (USATSI)

Braves - A wild one, no? It would be shocking but make a lot of sense. The club is already very familiar with Heyward, and it's a fan base that loves him. They are rebuilding, sure, but Heyward is only 26 and would still be in his prime when the team is making its expected turnaround. Not only that, they can definitely handle this financially, given how stripped down the MLB roster is.

Nationals - Jayson Werth's deal comes off the books after 2017. Heyward could man center field until then and shift to a corner once that happens. Yes, I know about the presence of Michael Taylor, but the Nats could use a big splash right now. Maybe this is it.

Mets - They lost out on Ben Zobrist but filled the second base hole with Neil Walker in a move that doesn't cost them extra money. They still need a center fielder and Heyward could shift to the corner when Juan Lagares is inserted. This kind of a move would definitely be a great signal to fans that the Mets are ready to step back into being a major free agent destination after their World Series run.

Yankees - Every sign says they won't be spending big in free agency this offseason, but it's the Yankees. Can we ever really count them out? We know they are shopping Brett Gardner, so if they aren't ready to start Aaron Hicks everyday -- or Carlos Beltran at his age and with those knees -- Heyward is a natural fit. Maybe a Beltran/Hicks combo in left with Heyward in right?

Mariners - It's hard to see the Mariners being able to spend this big right now, given their current contractual obligations, but this is a great fit. In right field at this juncture, the Mariners look to have a platoon featuring Seth Smith (likely with Franklin Gutierrez). Heyward is a big upgrade and fits nicely in the two hole behind Nori Aoki and in front of the Robinson Cano, Nelson Cruz, Kyle Seager, Adam Lind power. To reiterate, I'd be shocked if they spent this big this offseason, but that's what the mystery team madness is all about. Speculate away!

Tigers - They don't seem connected to any more big names after the Jordan Zimmermann signing, but the offseason leading up to 2012 is when we heard they wouldn't be signing any huge deals. They went nuts for Prince Fielder. During the Zimmermann press conference, owner Mike Ilitch noted that he doesn't care about spending lots of money, either. Their big hole is in left field right now, but they moved Miguel Cabrera to accommodate Fielder. They could do something similar again. If I had to mount a strong argument in favor of a mystery team, I think this would be my top choice.

Phillies - Finally not suffocating on long-term contracts to old players, the Phillies only have $23.7 million in guaranteed deals for the 2017 season. They are in a rebuild, yes, but they are planning to turn it around within the next two years and Heyward is only 26. He could slide right into right field and the centerpiece of the turnaround.

Dodgers - They'd need to trade away some of the outfielders they have in house, but they have far too much money to not list. Plus, the new front office is definitely a "new school" regime and these types love Heyward's well-rounded game.

? - It's the mystery team, baby. It could be anyone (well, not anyone -- sorry A's and Rays -- but it's a fun game to play)

The odds right now seem to favor Heyward landing with the teams 100 percent known to be involved -- Cubs and Cardinals feel like the favorites -- but we always have to watch out for the mystery team. They win with huge deals sometimes.