A spectacular refereeing error by Ali Kandil during the first-round game between Mexico and unfancied El Salvador left the latter side apoplectic.
The minnows had held out until the 44th minute and were awarded a free-kick deep in their own half.
But they watched in horror as Mexico's Padilla stepped up to take the kick, crossing for Valdivia to poke home the opener into an open goal.
The El Salvadoreans surrounded Kandil and his linesman, kicking the ball into the crowd and challenging the referee to book or send them off.
Kandil wisely blew for half-time. In the second half, El Salvador continued to kick the ball into the crowd as often as possible, and lost 4-0.