It's hard to maintain dominance for an extended period of time.
Pachuca's run as the best club in Mexico and one of the top clubs in the Western Hemisphere might be starting to crumble as America routed Pachuca 4-1 in the first leg of their Sudamericana series.
Pachuca needs to win by a large margin in Estadio Azteca to have a shot of defending their Sudamericana title.
This should serve as a wake-up call to DC United. Regardless of league form, if you're not careful against a well-prepared and motivated team, this can happen.