Mauro Boselli and Luis Montes netted late goals on Saturday to send Leon through to the Liga MX Apertura semifinals, just as 10-man Club Tijuana looked set to record a famous comeback victory.
Xolos raced to a 3-0 lead at half-time to tie the series 3-3 on aggregate and would've gone through due to finishing higher in the regular season, but Boselli headed in nine minutes from the end and Montes made the final score 3-2, with the aggregate 5-3 in favor of Leon.
Had Club Tijuana held on, it would've been the first time since Mexico's short two-tournaments-a-year setup began in 1996 a side had overturned a three-goal first-leg deficit.
Colombian Dayro Moreno opened the scoring from the penalty spot in the 13th minutes, but Xolos' hopes seemed to sour when Juninho was shown a red card three minutes later. In the 10th minute, Tijuana coach Miguel Herrera had been sent off from the bench for arguing with the referee.
Defender Yasser Corona put Tijuana further ahead in the 41st from close-range, with Guido Rodriguez netting what appeared to be the crucial third goal two minutes later.
Leon had comfortably won the first leg 3-0 last Wednesday in Estadio Leon and came into the game on a run of 11 undefeated games since Argentine coach Javier Torrente took over.
Tigres thrashed Pumas 5-0 earlier Saturday to book their place in the semifinals, while Chivas host America and Pachuca faces Necaxa in the last two quarterfinals on Sunday.