Fading Mexican champions Pachuca had three sent off as they slumped to a 3-1 defeat to Monterrey, who also had a player dismissed in a stormy game.
Pachuca coach Enrique Meza criticised his team after Argentine forward Damian Alvarez and Mexican internationals Jaime Correa and Fausto Pinto were shown the red card in the last half hour of Saturday's match.
"We did enough to deserve the defeat," said the former Mexico coach. "Our conduct left much to be desired, we stopped playing and tried to win the game on the base of... mis-channelled aggression."
Chilean international Humberto Suazo gave Monterrey a 27th minute lead but Christian Gimenez levelled two minutes later for the Beavers.
Despite having Jesus Arellano sent off for dissent in the 37th minute, Monterrey went back in front with another Suazo goal before Luis Perez completed the scoring with an injury-time penalty.
Alvarez was sent off for fighting, Pinto for an ugly foul and Correa for protesting the penalty award as Pachuca lost their heads.
Pachuca, the CONCACAF champions, are third in Group One with 19 points from 14 games and Monterrey and fifth in Group Two with 13.
Santos Laguna stayed top of Group Two with an impressive 5-2 win at Atlas, Group One leaders Toluca drew 0-0 at Chiapas and Morelia gave new coach David Patino a winning start by beating Tigres UANL 1-0.
Cesar Luis Menotti's Tescos UAG squandered a halftime lead as they went down 3-2 at home to San Luis. Colombian forward Tressor Moreno scored twice as the visitors struck three times in 14 minutes in the second half.
The win took San Luis top of Group Three and left the Owls bottom of Group One.
