Europe's superclubs have been faced with an odd problem this summer. All across the continent, top clubs have tried to move players viewed as no longer worth their paychecks — and have been unable to sell.

At Real Madrid, manager Zinedine Zidane did his best to humiliate Gareth Bale into leaving, but Bale remains in Madrid, with the transfer window closing on Monday. Antonio Conte did the same to Mauro Icardi at Inter Milan, with the same result. Meanwhile, Manchester United had to spend big money just to get someone else — Inter, in this case — to take Alexis Sanchez on loan.

Even the best of the rest are selling, not buying. For example, Ajax reached the Champions League semifinals last year, but then in the offseason it sold its best two young players —Matthijs de Ligt to Juventus and Frenkie de Jong to Barcelona — for a return of about $150 million.

Such is the state of the European game. The only thing holding back the top clubs is their inability to sell the world-class players they already have in order to buy more of the best players from other teams. At some point, this system may be too top-heavy to avoid toppling over.

Short takes

• The U.S. and Mexico met just two months ago in the final of the Gold Cup, but to compare the teams' immediate future, their friendly next Friday might provide an even better look. Mexico's biggest stars, such as Hirving Lozano, Hector Herrera and Javier "Chicharito" Hernandez, are all back on its squad, while the U.S. is bringing its brightest young stars. Trophies aside, a U.S. victory would be a boon for the squad's confidence.

• In France and Brazil this week, referees stopped first-division games because of homophobic banners or chants from the stands. In France, which instructed its referees to pause games in such circumstances this year, it happened in both Ligue 1 and Ligue 2. Why doesn't Mexico, where homophobic chants at goal kicks are routine and the Mexican soccer federation has been fined repeatedly during national-team games, adopt the same zero-tolerance approach?

WATCH GUIDE

Seria A: Roma at Lazio, 11 a.m. Sunday, ESPN2. Since the two Rome clubs last played in a 3-0 Lazio victory last spring, Roma has changed just about everything. It has a new coach, new sporting director and practically a new team on the field. Lazio, meanwhile, is more or less settled, with few changes. The Derby della Capitale is always pulsating, but it might be come too early for Roma, with all the team's changes.

Writer Jon Marthaler gives you a recap of recent events and previews the week ahead. E-mail: jmarthaler@gmail.com