Why haven't some of baseball's biggest free agents signed yet?

Your eyes do not deceive you. The market for top free agents is developing more slowly than usual -- more slowly than it has during any of the four offseasons since baseball introduced the qualifying offer in 2012-13.

Thirteen of the top 20 free agents remain unsigned, using the list compiled by MLBTradeRumors.com. On this date last year, only three of the top 20 were unsigned; in each of the two years before that, a mere eight were.

Things will sort themselves out during the next two months leading to spring training, and right up to Opening Day. But the reasons for the deliberate pace are worthy of exploration -- as are some possible solutions.

First, the reasons:

The qualifying offer

Among the 13 top free agents who remain unsigned, nine received a qualifying offer, which this year was valued at $15.8 million.

Right-hander Mike Leake and left-hander Scott Kazmir both were ineligible for QOs after getting traded last season. Outfielder Yoenis Cespedes also was ineligible due to his contract, as was righty Kenta Maeda, who is coming from Japan via the posting system.

The threat of losing a draft pick surely gives teams pause on certain free agents -- most likely right-handers Ian Kennedy and Yovani Gallardo, perhaps even outfielder Dexter Fowler, shortstop Ian Desmond and second basemen Daniel Murphy and Howie Kendrick.

The attachment of a pick, however, should not affect some of the top players on the market – players such as outfielder Justin Upton, first baseman Chris Davis and outfielder Alex Gordon.

Teams that are not spending big.

The list includes a number of prominent high-revenue clubs.

The Yankees seemingly are waiting for some of their big contracts to expire. The Angels do not want to cross the $189 million luxury-tax threshold. The Rangers made their big investment when they traded for left-hander Cole Hamels.

The Mets rarely spend big. The Phillies are rebuilding. The Dodgers made a major run at Zack Greinke, only to get outbid by the Diamondbacks, and nixed a $45 million deal for Hisashi Iwakuma due to concerns over his physical.

Might the Yankees, Angels and some of the others jump? Well, a few of them should; the free-agent market next off-season will be notably weak. The Cubs, by signing outfielder Jason Heyward, infielder Ben Zobrist and right-hander John Lackey, took the long view, figuring they were spending not just for one but two years.

Teams that are "tanking."

Oh, no one will dare use that dirty little word, but the Braves, Brewers and Reds essentially have made every player on their rosters available, flooding the trade market with alternatives to expensive free agents.

The Phillies are in the same, er, rebuilding, mode. And the Rockies are another team willing to trade almost anyone.

The trade market overall.

Say you're a team looking for an outfielder. Justin Upton and Cespedes are appealing -- Upton, 28, is just two years older than Heyward, and a more accomplished hitter. But the trade options include: The Rockies' Carlos Gonzalez, Charlie Blackmon and Corey Dickerson; Dodgers' Andre Ethier and Carl Crawford; Yankees' Brett Gardner; Braves' Ender Inciarte and Reds' Jay Bruce.

Likewise, say you're a team looking for a starting pitcher. Leake, Maeda, Kazmir and lefty Wei-Yin Chen are among the remaining free agents. But the trade options include: The Indians' Carlos Carrasco and Danny Salazar; Rays' Alex Cobb, Jake Odorizzi and Drew Smyly; Padres' Tyson Ross, Andrew Cashner and James Shields.

The Dodgers, active in both markets, could trade for one starter and sign another. But to hear rival executives tell it, the trade front is full of obstacles. The Indians do not want to trade a starter. The Padres are setting unrealistic demands, as are the Marlins with Jose Fernandez. And the Rays, at least for the Dodgers, will not be an easy partner; they might be reluctant to trade with their former GM, Andrew Friedman, and beyond that likely value players the same way.

Now, some solutions:

Patience

Seriously, does anyone expect Cespedes and Upton to be unemployed in 2016? What about Murphy and Kendrick, even Gallardo and Kennedy?

Some of those free agents might not get the contracts they desire, but that happens in every market -- and the potential for such disappointment was especially acute this offseason, considering the number of quality players available.

Still, it's reasonable to be skeptical of claims that the money is drying up, that there are not enough teams left to spend. The Nationals "found" $210 million for Max Scherzer last January. The Padres "found" $75 million for James Shields in February. And did anyone expect the Diamondbacks to come up with $206.5 million for Greinke earlier this month?

The Dodgers, Nationals and White Sox are among the teams that, in the perception of rival executives, could do something big. The Orioles offered Davis a reported $154 million; they will spend a percentage of that if he departs. The Cardinals have yet to do anything of major significance, and -- like the Nationals -- offered Heyward $200 million.

Modified tanking

Yes, that's an oxymoron, sort of like, "fragrant stench." But if you're the Phillies - sitting on a ton of money, holding a protected first-round pick, knowing next year's market is weak -- why not take the plunge and make a strategic signing?

Upton would be perfect; he's young enough to still be a force by the time the Phillies return to contention. Desmond, because of his leadership abilities, also could make sense. Even a starter such as Leake could help stabilize the rotation while the team's younger pitchers develop.

The Braves seemingly have flirted with such a strategy as they prepare for the opening of their new ballpark in 2017, showing interest in Zobrist and free-agent reliever Darren O'Day, among other veterans. Agents, though, are skeptical whether the team actually wants to spend; the Braves' most expensive signing thus far is catcher Tyler Flowers at two years, $5.3 million.

An aggressive plunge into the market would make less sense for low-revenue teams such as the Brewers and Reds.

Sign and trade

The concept, at least to this point, is foreign in baseball. But it could be one way for a team with an unprotected pick, outside the top 10, to acquire a select free agent without losing its first-round choice.

Here's how such a pre-arranged deal would work: A team with a protected pick would sign a free agent saddled with a qualifying offer, a free agent desired by another club.

The signing team, with the free agent's consent, then would trade the player to the club that wants him, a club that presumably would give up prospects in return.

The player would get to a place he wants to go. The signing team would get players who are closer to the majors than a draft pick. And the trade partner would retain its first rounder.

The arrangement, under the collective-bargaining agreement, would be perfectly legal. But chances are no free agent will be desperate enough to require such a lifeline, and no team will go to such lengths to acquire a player.

Patience - the pace will pick up. Bargains are coming, but so are more big signings.

Last we checked, no one is going hungry in this sport.