MEXICO CITY -- Enrique Bonilla isn't known for being brash. The Liga MX president is more comfortable in the day-to-day decision-making of running Mexico's first division than he is in front of the media. But when it comes to the alliance between Liga MX and MLS, Bonilla is direct: he's adamant that the partnership is going to impact club soccer in North America in a major way.

"A huge success for sports in the United States and a huge success for football in Mexico," is Bonilla's take on what's ahead for the partnership.

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The statement could be construed as hot air from a league president trying to get some attention, but it's worth taking a step back and considering just how big a claim it is, especially coming from the usually coy Bonilla.

Equally, it's worth considering how these two leagues could be a lot more intertwined in the future.

The relationship between MLS and Liga MX has intensified following the March 2018 announcement of a strategic partnership between the two, much more so than during the SuperLiga summer tournament that was held between 2007 and 2010. It has so far given rise to the birth of Campeones Cup, a one-off game featuring the MLS champion and Liga MX's Campeon de Campeones, and a potential All-Star game to be played further down the line.

Last May, the next stage of the partnership was unveiled with the inaugural Leagues Cup, featuring four teams from both leagues and culminating on September 18 with Cruz Azul beating Tigres in the final in Las Vegas.

Reception to the tournament has been lukewarm -- particularly after MLS teams didn't field full-strength teams due to scheduling issues -- but the future of this partnership goes a long way beyond Wednesday's final in Las Vegas.

According to what MLS commissioner Don Garber told ESPN last month, the "ultimate dream" is "a league that is combined in some way." So far, nobody seems to be shutting the radical idea down. The opportunity and momentum for collaboration off the back of the joint 2026 World Cup in the United States, Mexico and Canada has started to gather pace.

In fact, after collecting a range of opinions from owners, GMs, coaches, players and those involved in negotiations between Liga MX and MLS, the will to push the partnership forward is striking.

The nascent Leagues Cup competition features MLS and Liga MX teams and will test the waters for increased competition between the two leagues. John McCoy/Getty Images

Baseball providing inspiration for MLS, Liga MX

"Everything is possible in this world," Bonilla told ESPN FC in Liga MX headquarters in Toluca recently when asked about plans for a joint league.

First up, it's worth pointing out that there isn't anybody sitting in a darkened office drawing up potential plans of how a league with 50 top-flight teams -- 30 from MLS, 20 from Liga MX -- could work. But that doesn't mean that the concept of a league that "is combined in some way" isn't guiding the alliance.

One idea gaining some early momentum, according to ESPN FC sources, is some form of interleague play like in Major League Baseball. The question of whether Liga MX and MLS teams could play each other in the future in regular-season play, like baseball franchises from the American League and National League do in the U.S., has been raised.

In MLB, teams from the two leagues didn't meet in regular-season play until 1997, over 90 years after it was first suggested. Before that, MLB teams from the two leagues only met at the World Series, or in exhibition games.

Interleague play with real points at stake would guarantee competitive games that matter. It may sound like a huge jump and there's a long way to go before it is consolidated as a fully formed vision, but if a 16-team and then a 32-team Leagues Cup tournament -- which is the goal for 2021 or 2022, with Bonilla also adamant that some games will be played in Mexico -- proves logistically possible and commercially successful, transferring that into actual league play isn't a giant step. And the concept of a Leagues Cup winner wouldn't necessarily have to be ditched.

The advantage of interleague play as opposed to a united league is that each league's structure and regulations -- salary caps, relegation, split seasons (in Liga MX's case), etc. -- wouldn't have to be fully in sync to make happen.

Atlanta United beat Club America in the Campeones Cup, which had a TV audience of 1.5 million. Dale Zanine/USA TODAY Sports

The Campeones Cup between the champions of both leagues, in theory, would subsequently grow in importance as the rivalries develop between the teams and leagues, becoming a World Series of sorts for North American soccer. The TV audience for the most recent edition between Atlanta United and Club America reached 1.5 million -- three times bigger than the recent "El Trafico" between LAFC and LA Galaxy.

But while the idea of combined league play and even a united league is still a ways away, the focus right now is on developing, expanding and improving Leagues Cup to "test the waters," according to one source close to the negotiations. Next year, eight teams from each league will qualify for the competition and there is a belief that MLS clubs will, given time to prepare and knowing about the tournament before the preseason, be more willing to field their first XIs.

"I think the MLS teams will see the tournament in a different way, now they realize that we sent the best we have, they have to realize that they have to send the best they have," said Bonilla.

The growth between MLS and Liga MX is partly based on the deep relationship between commissioners Don Garber and Enrique Bonilla. Daniel Clark-USA TODAY Sports

Why the partnership makes so much sense

To be one of the top leagues in the world has long been the unashamed goal for MLS, while Liga MX has largely existed in a bubble as one the strongest leagues in CONCACAF and one of the richest in the Americas. Liga MX's significant internal market -- Mexico boasts the world's 15th largest economy -- is bolstered by the natural foreign enclave of dollar-wielding fans spawned from migration to the United States, where close to 40 million people of Mexican heritage reside.

The North American market is complicated by the "big four" sports leagues in the United States: NFL, NBA, MLB and NHL. But changing demographics and habits in the United States see soccer as tied for the second-most popular sport to watch for 18-to-34-year-olds, according to a 2018 Gallup poll.

"As MLS is growing to 30 clubs and Liga MX is still the most-watched league in the United States, there's a lot of potential there for a massive audience in 5-10 years' time if [Liga MX and MLS] can capitalize on the momentum of the 2026 World Cup," said Scott Minto, director of the Sports MBA program at San Diego State University.

For MLS owners, the fact that Liga MX has the highest TV ratings in the United States is of huge appeal. A total of 4.8 million in the United States watched the Liga MX 2018 Clausura final between America and Cruz Azul. More people in the United States tune in to watch Liga MX each weekend than the Premier League, and while MLS has made gains, it's yet to meaningfully close the gap on either of the aforementioned leagues.

Another asset for Liga MX is the existence of historic superclubs like Chivas and Club America. Las Aguilas have a bigger social media following than the Dallas Cowboys, while Chivas have more than all but three NFL franchises and a superclasico friendly earlier this month had an attendance of over 61,000 fans in Chicago.

For Leagues Cup, the attendance in Houston for the quarter and semifinals -- 20,315 and 22,532 -- was higher than the Dynamo has managed for any MLS game this season.

On the other side of the partnership, owners of Liga MX teams understand the benefits of growing the league in the United States, a market with greater consumer power than Mexico. But they're also aware of the value that MLS franchises possess. LAFC and New England Revolution were valued higher in a 2018 Forbes report than Chivas, Club America and every other Liga MX club. Thirteen MLS clubs made the list of top 50 most valuable clubs in the Americas, compared to 11 Liga MX institutions. That may not sound like a vast difference, but the rise in value of MLS franchises has been meteoric due to the increased demand from ownership groups to be part of the league.

With the 2026 World Cup on its way to the United States, Mexico, and Canada, the countries' leagues are hoping to take advantage of the momentum. EPA/SERGEI CHIRIKOV

"Tactically and technically, [MLS clubs] may be one or two rungs below [Mexican clubs], but in questions of administration, organization, infrastructure and understanding sport as a business, I think that they are a lot more advanced than us," said Ricardo Zayas, director of the Johan Cruyff Institute in Mexico City.

The number of obstacles when considering a deepening relationship between MLS and Liga MX appear overwhelming. Building this "slowly but firmly," as Bonilla repeats, makes sense and entices owners.

Other roadblocks could be the different schedules that the leagues operate on, as well as getting the thumbs up from FIFA and CONCACAF, who would both have to be on board and grant approval. Add to that list the problems of a disaster club like Liga MX's Veracruz; potential resistance from some Liga MX fans, who perceive MLS as being a step down; the instability at times within Liga MX ownership; bringing the players' associations on board; the travel and associated costs; MLS' poor record in matchups on the field; keeping owners onboard; and how to introduce interleague play with the uneven number of teams in each league.

But while there are impediments, there is no single impediment to definitively end the project. And while that remains the case, the push toward an expanded Leagues Cup, potential interleague play and even a united league is set to march on.