Fredy Montero was a two-time top scorer in the Colombian leagues and had already made three senior national team appearances as a 21-year-old in 2009. He picked the expansion Seattle Sounders over a Spanish club, Real Betis, and several Mexican teams. Montero said of M.L.S., “I felt it was a good place to prepare me for my future, which may be in Europe.”

At 18, Fabián Castillo was one of the top prospects in Colombia when he decided in March 2011 that Dallas would be the best place to develop. He rejected advances from the Portuguese powerhouse Benfica and the Italian Serie A club Brescia.

Darren Mattocks, 21, a forward from Jamaica, opted for M.L.S. over the Danish club Brondby, joining the 10 Jamaicans regularly called to their national team who are already in the league.

“I always wanted to go to Europe right away, but I thought M.L.S. would be a good starting point for my career,” Mattocks said. “It was a better offer and it was closer to home. Denmark is so far away from Jamaica.”

As M.L.S. has solidified and grown, money for better talent has become available.

“Players like Montero are in an economic space that we just weren’t in four or five years ago,” said Todd Durbin, the league’s executive vice president. “We’re in that space today, and it’s connected us with the global community.”

M.L.S. stimulated its clubs’ entry into the highly speculative market for young international prospects with favorable terms. While veteran designated players — the league’s dispensation program for pricey stars — count against the salary cap at $350,000 each, no matter how much they make, designated players who are 23 or younger count for only $200,000 and those under 20 count for $150,000.