Franco Arizala struck in the 68th minute for Leon as they claimed a 2-1 win at home to Flamengo in Group 7.
Flamengo fought hard after being reduced to 10 men early on and equalised despite their numerical disadvantage, only to concede midway through the second half.
Liga MX Apertura champions Leon, who have made a slow start to the Clausura campaign, were given an early advantage when Amaral was red-carded on 12 minutes.
Mauro Boselli gave them a 32nd-minute lead from the penalty spot, sending Flamengo goalkeeper Felipe the wrong way.
Flamengo levelled two minutes before half-time through Victor Caceres, who headed in Elano's set-piece.
Substitute Arizala scrambled in the winner after Boselli had missed another opportunity from the penalty spot on 61 minutes.
Peruvian outfit Real Garcilaso staged a second-half comeback on their way to a 2-1 win over Cruzeiro at the Estadio Huancayo.
Bruno Rodrigo put the Brazilian visitors in front with a 20th-minute header, but their advantage was gone early in the second half.
Ezequiel Britez volleyed in a corner at the back post seven minutes after the interval and the scoring was complete thanks to Ramon Rodriguez not long after the hour-mark.
It was another set-piece which led to the winner as goalkeeper Fabio was caught in no man's land and saw Rodriguez tap in on 62 minutes.
Marcelo Zalayeta netted a second-half equaliser to earn Penarol a point in a 1-1 draw at Deportivo Anzoategui and Deportivo Cali edged Cerro Porteno 1-0.
