Julio Urias

Julio Urias, shown pitching at the All-Star Futures game at Target Field on July 13, is still in the Dodgers organization after Thursday's trade deadline. (Elsa / Getty Images / July 13, 2014)

In the days leading up to last week's trade deadline, a new conventional wisdom floated throughout baseball. The hoarding of prospects had gone too far, or so the theory went, and savvy general managers would pounce on the chance to trade away even the most promising minor leaguers for veterans that could make a difference in this year's pennant race.

The evidence for the theory: On July 5, the Oakland Athletics had traded shortstop Addison Russell, ranked as one of the top five prospects in all the minor leagues, in a package deal for pitcher Jeff Samardzija.

As it turned out, it was just Billy Beane being Billy Beane. The maverick Oakland general manager traded his star prospect, but he also traded his cleanup batter, Yoenis Cespedes.

The number of Baseball America top 50 prospects traded on Thursday's deadline day: 0.

For all the breathless anticipation about which of baseball's elite prospects would be moved at the deadline, none were.

The Dodgers had very real pitching needs, and they had three of baseball's very best prospects in outfielder Joc Pederson, infielder Corey Seager and pitcher Julio Urias. The Dodgers still have the needs, and they still have the prospects.

"If we didn't think Joc, Corey or Urias had a chance to be impact players, they'd be out of here," Dodgers General Manager Ned Colletti said.

The key word there is "chance." If one of the three develops into an impact player, the Dodgers will be in line with historical odds.

Urias ranked No. 13, Seager No. 16 and Pederson No. 18 on the Baseball America list.

The players in those spots in 2008: Jacoby Ellsbury, Brandon Wood and Mike Moustakas. In 2009: Moustakas, Giancarlo Stanton and Logan Morrison.

Of the top 50 prospects, agent Scott Boras says his research suggests 15 might turn out to be impact players. So why were none of those top 50 traded on Thursday?

The economics of the game have tilted the value of prospects to an all-time high, and not just because of the never-ending escalation in the salaries of free agents.

As revenue sharing enables small-market clubs to keep their star players – Paul Goldschmidt with the Arizona Diamondbacks, Joey Votto with the Cincinnati Reds, Felix Hernandez with the Seattle Mariners, and so on – the free-agent pool gets older and less attractive, even as the limited supply pushes salaries higher.

And, with recently imposed limits on how much teams can spend to sign draft picks and international players, a team no longer can trade a prospect and replace him by investing more in the amateur market.

"There is a logjam on those players that are deemed prospects," Boras said. "Teams that are successful and have the money to spend can't spend the money on young players. That is creating an artificial value."

So too is the flood of long-term contracts signed by young players. The Boston Red Sox acquired outfielder Allen Craig from the St. Louis Cardinals on Thursday, in a trade for pitcher John Lackey.

Craig might not have as high a ceiling as, say, Pederson. But Craig is signed for three years beyond this one, at a relatively reasonable $26 million, and the Red Sox do not inherit the risk of a prospect going bust.

"Control at a discounted price is why teams are signing those players so early," Boras said. "It makes them very tradeable."

The relative inefficiency of free agency and the restrictions on amateur spending limit opportunities to acquire a premium player at a young age. Relief pitchers and bench players and bottom-of-the-lineup hitters are available at reasonable cost, but there are far fewer chances to acquire an impact player rather than develop one.

"The value of a premium and/or close-to-the-big-leagues prospect with highest ceiling is huge in today's market," Angels General Manager Jerry Dipoto said.