Josef Martinez says Atlanta United is his Barcelona, his Real Madrid. He feels at home, he’s scoring goals and his bank account just got a whole lot fatter. The next five years of his life and the prime of his career belong to the Five Stripes. For Martinez, MLS is a league of choice.

Atlanta made Miguel Almiron a champion, paid him well too. He’s worth many millions of dollars. Exactly how many is a matter of perspective, but Almiron’s time is coming. He will be sold, it seems certain, during this window or the next. For Almiron, MLS is a selling league.

So which is it? For years, we were told MLS should and would strive to be the former, a destination rather than a stepping stone. Then Commissioner Don Garber said in December, during his annual State of the League address, that the league must become more of the latter.

It’s both, and it seems to me the future of MLS looks a whole lot like Atlanta’s offseason. From here on out, the most successful clubs will be the ones who master the delicate balance between ambition (buying) and investment (selling), from Designated Players all the way down through the academy.

The pressure, more than ever before, is on executives to strike that balance, and the eyeballs this offseason are on Atlanta. By re-signing Martinez, they’ve passed their first test with flying colors.

His new contract falls on the ambition side of the fulcrum. In Atlanta, Martinez is a star, beloved by a fanbase and a city who expect that he’ll deliver more trophies. In Atlanta, it makes sense for a rising South American star to devote his future to the club as he prepares for World Cup qualifiers and the best years of his career.

Martinez chose to stay in MLS because it was the best thing for his career. That should be celebrated, as should owner Arthur Blank’s determination to raise the standard across the league.

Blank, with the help of club president Darren Eales and technical director Carlos Bocanegra, proved Atlanta can be a club of choice, a major player in the international transfer market. Blank’s $30 million-plus investment in transfer fees to date alone proves that. The ability to attract Almiron in the first place proves that. The ability to lock Martinez in long-term proves that. Signing "Pity" Martinez would prove that, too.

What Atlanta haven’t yet proven is that they can sell, that they can monetize their unprecedented investments in a way that doesn’t inhibit their ambition and that the lure that helped convince Almiron to come to Georgia will pay off.

Because for Almiron and Ezequiel Barco and the next starlet Eales and Bocanegra lure north from South America or develop in the academy, the next move matters. Europe is beckoning, with transfer fees that can change a club or sustain a prolonged period of dominance. As Garber extolled before MLS Cup, there’s nothing wrong with being a middle man.

Atlanta know this, and their transfer model and recruitment policy require they deliver, whether that’s now or in the summer and perhaps with a little maneuvering in the meantime, as Sam Stejskal explained a few days ago. They don’t need the money, per se, but they do need to send a message to the rest of MLS and the world.

It’s why you see Eales, no stranger to the posturing and politics of the transfer market, so doggedly insisting on $30 million for the 24-year-old Paraguayan. It’s why Barco’s place in the Argentina U-20s ahead of the World Cup is such a hot topic of conversation. It’s why Greg Garza was traded to give George Bello, a young American left back with plenty of European interest, an opportunity to realize his dream and create value for the club.

“Our model was always that we could attract players that wouldn't see it as the end of their careers,” Eales said. “Clearly, we can attract players from the younger age group. The challenge now for the league is, while there will be special players who want to go and play for the world's top clubs, can we retain some of those players? Josef is a good example.”

Eales is right. Josef is a good example, but there’s very little time to celebrate. Almiron is the next example, and the delicate balance between ambition and investment never ends.

Can Atlanta sell as well as they buy? That question may define their season, and it may very well define the future of MLS.