America fell to third place in the Liga MX after losing to Atlas as rivals Tigres and Tijuana won to bring their records to a perfect 4-0.
The 2-1 loss was America's first of the Clausura 2013 season.
Tigres won 1-0 on the road against Queretaro and Tijuana dominated visiting Pachuca 2-0.
Tijuana and Tigres are set to play each other next week. Cruz Azul, which routed Puebla 4-0 on Saturday, is the only other undefeated team.
Atlante beat Chiapas 4-3 in a scoring duel for its first victory of the season after three defeats, while UNAM Pumas finally put one on the win column thanks to a 1-0 away triumph over Toluca.
Chiapas, Chivas de Guadalajara, San Luis and Leon remain winless.
Atlas moved ahead of Queretaro in the contest to avoid relegation and Chiapas replaced Atlante in the cellar. EFE