Colombia Wrap: Medellin's perfect record dashed
Aguilas Pereira led heading into the final 10 minutes of their hosting of Medellin, before the Group B leaders equalised in a 2-2 draw.
Hernan Torres' Medellin led courtesy of German Cano's first-half goal, but two goals in four minutes from Aguilas pair Brayan Angulo and Maicol Balanta saw them turn the tie on its head.
But Elton secured a point for Medellin with his 81st-minute equaliser, which also ended Aguilas' chances of progression.
With two matches remaining in the semi-final group stages, Medellin are six points clear of second-placed Deportes Tolima - requiring just one more point to secure a final spot.
Tolima beat Deportivo Cali 4-2 to join them on four points, and helping Medellin open a significant gap at the top.
David Silva's first brace in the league helped Tolima go three goals clear after Hector Acuna's opener.
Cali fought back gamely to make it a one-goal game after Helibelton Palacios and Carlos Rivas struck, only for Davinson Monsalve to restore Tolima's handy lead.
There was only one goal scored in the two Group A fixtures, with Luis Paez's winner for Atletico Nacional (six points) against Once Caldas (three) helping them fight back into final contention.
After two straight losses, Atletico Nacional needed points to stay in touch with leaders Santa Fe - and their second victory of the group stages took them within two points of top.
Santa Fe (eight points), meanwhile, were held for a second straight outing, Atletico Huila (five) earning a 0-0 draw away from home.
All four sides remain mathematically alive to finish top in Group A.