Can a Mexican final four be prevented?

This week the CONCACAF Champions League resumes with the knockout stage as Columbus Crew, Marathón, Comunicaciones, and Arabe Unido face off against Toluca, UNAM, Pachuca, and Cruz Azul, respectively. It's going to be very difficult for the any of the first group of four to progress, and anything other than a win in their home leg all but gives the tie to their Mexican opponents.