There are three ways for a team to build: free agency, drafting and trading.

With a stated budget of just over $100 million, Sandy Alderson’s free-agent options are limited, especially if he dives into the deep end of the Jose Reyes pool. He’ll be looking to plug holes in the bullpen and rotation with middle-tier talent. Cheap bench players are always available.

There is potential in the minor league system, but it is the lower minors, which the Mets want to avoid delving into. Solid drafting is the best way to lay the foundation and the Mets are making progress in that direction and figure to keep their young talent.

That leads us to trading, and things aren’t rosy in that department, either.

David Wright, who has been in decline the past two seasons, has the biggest upside and a manageable contract. He’s a cornerstone, especially if Reyes leaves, and the player who intrigues other teams, believing a change of scenery would benefit him. A Wright trade would mean serious re-building for the Mets, but he’s the player who would bring the most in return.

Trading him is a franchise-defining decision.

Other than Wright, what is the market value for some of the others?

Josh Thole: Young, inexpensive with more potential than production. Thole did not perform to expectations and wouldn’t draw attention from a team wanting a starting catcher. Teams needing a catcher have more experienced options in the free-agent market. It’s hard to believe anybody would trade for him to be a starter.

Ike Davis: Could be attractive, but after missing much of the season with an ankle injury he represents a risk. Young, inexpensive and loaded with potential – if healthy – he’s the ideal piece for the Mets to keep and build around.

Ruben Tejada: Impressed a lot of scouts and would draw interest, but the Mets will need him at shortstop if Reyes goes or at second if he stays. He’s not going anywhere.

Jason Bay: You must be joking. People are saying all the time that the Mets should trade Bay. What planet are they on? Bay has not played well since signing as a Met; he’s been injured and has a hefty contract. Can you see the line forming now? The Mets have two hopes for him: 1) he stays healthy and meets expectations to salvage the final two years, or 2) if that doesn’t happen, then he doesn’t get the necessary at-bats and games for his option to kick in. Two more years.

Angel Pagan: Regressed this year to the point where the Mets might not tender him. He’d sign somewhere as a bench player, but nobody will trade for him.

Lucas Duda: Scouts love his power potential and he played decent defense in right field. He would be part of a larger package, but wouldn’t be someone teams would want to trade for to build around. Besides, the Mets’ outfield forecasts as weak, so he’s getting the full time shot in right.

Fernando Martinez: Had been sought after in previous years, but is a fragile, injury risk whose value has declined. Too bad they can’t turn back the clock two years. If the Mets can swing something with him, they should do it, but his real value to them would be to stay healthy and reach his potential, which is becoming less and less likely.

Johan Santana: Nobody knows how healthy he is, which means he’s staying put for now. Should Santana come back and be solid and healthy in the first half, you could see the Mets trying to deal him if they aren’t in contention. Even if they were, they might pull the trigger on a trade to free up salary. This bears watching, but not until June and July.

Mike Pelfrey: Has a manageable contract and is young. He regressed this season, but there’s still potential for the right pitching coach. But, if they trade him, he would thin out an already spotty rotation. The Mets will keep him and hope he improves. If not, then it might be time to cut him loose. There could be takers at the trade deadline.

Jon Niese: Coming off an injury and who knows if he’d pass the physical? Mets love his potential, so he’s not going anywhere.

R.A. Dickey: Teams don’t trade for journeyman knuckleball pitchers in the off-season. They wait for the trade deadline. He’s been arguably the Mets most consistent starter, but he’s a No. 4 according to most scouts, maybe a No. 5. He’s somebody a contender might covet in July, but he’s not going to bring back a lot of talent.

Dillon Gee: Surprised a lot of people this season. But, the pitching deficient Mets won’t move him. After a great start, Gee had a rocky second half, which makes him a question to the Mets, not to mention any team with interest.

Bobby Parnell: Young and a power arm is always attractive. Not so much is his command and thought process on the mound. There are no assurances the Mets will make him their closer as there are numerous reports saying that is their greatest need. If Parnell can’t convince the Mets he’s closer worthy, then what must other teams be thinking? Right, he’s a bullpen piece who needs a lot of work. Not a long line here.

So, if you look at the Mets’ trade options, dealing Wright would net the most, but you have to wonder what considering he’s several years removed from his best season. There are limited other options to deal and they are most suited for moving at the trading deadline.