Own goal beats beleaguered America
Atlas were lucky to score in Saturday's match at the Jalisco stadium in Guadalajara when a shot by Atlas defender Mario Mendez hit Juan Carlos Valenzuela on the head and was deflected into keeper Guillermo Ochoa's net in the 58th minute.
America's Paraguayan forward Salvador Cabanas has been in hospital for 14 days after being shot in the head during an argument in a Mexico City bar.
His team-mate Juan Carlos Silva took a bullet to the buttocks in an attempted robbery a week ago.
Goal-shy Cruz Azul, runners-up to Monterrey in the Apertura championship in December, were upset 2-0 at home by Santos Laguna, who scored through Colombian Carlos Darwin Quintero and Argentine-born forward Matias Vuoso.
Cruz Azul, whose Argentine striker Emanuel Villa was top scorer in the Apertura with 19 goals, have found the net once in four Clausura matches.
Guadalajara are the only team with a maximum 12 points after their 2-0 win over Queretaro on Friday night.
Striker Javier Hernandez scored their second goal to take his tally to a championship-leading seven in four matches.