The top two clubs in the Colombia Primera A both lost at home in round seven, opening up the Apertura championship race.
League leaders Santa Fe suffered their first defeat of the campaign, losing 1-0 to Millonarios, while second-placed Atletico Nacional succumbed to La Equidad 2-1.
Santa Fe and Nacional's losses saw the top six clubs finish the weekend within two points of each other, as Once Caldas, Junior, Boyaca Chico and La Equidad all won.
At the Estadio Nemesio Camacho on Saturday, Millonarios won thanks to Andres Cadavid's 42nd-minute goal with the 28-year-old defender side-footing the ball into the net from Dayro Moreno's driven cross, after a corner from the visitors was partially cleared by Santa Fe.
Millonarios moved up to seventh with 11 points after extending their unbeaten streak to four games, while Santa Fe remain on 16 at the top of the standings.
Nacional missed the opportunity to move ahead of Santa Fe later on Saturday as they failed to reel in La Equidad in the second half at the Estadio Atanasio Girardot.
After a goalless first half in Medellin, La Equidad took advantage of a defensive error two minutes after the break to open the scoring.
Nacional defender Alexis Henriquez missed a cross from La Equidad's Fredy Hinestroza and the ball found Leonardo Villagra, who set up Jose Moreno to score off the post.
La Equidad's second goal came in the 58th minute with Hinestroza scoring from the rebound after Villagra's initial shot was saved by Nacional goalkeeper Cristian Bonilla.
Diego Arias' stunning long-range free-kick in the 78th minute gave the home side some hope of a draw.
But as the minutes passed by, Nacional's frustration increased with Arias receiving a red card in the 94th minute.
Nacional remain second on 15 points, ahead of Once Caldas on goal difference with the latter beating Deportes Tolima 3-0 on Sunday.
Junior moved up to 15 points with a 1-0 win against Deportivo Cali, while Boyaca Chico completed the quartet of clubs a point behind Santa Fe with a 3-2 triumph over Uniautonoma.
In other results in Colombia's top tier, Atletico Huila defeated Alianza Petrolera 3-0, Fortaleza drew 2-2 with Patriotas Boyaca, Envigado won 2-1 at Deportivo Pasto and Itagui completed a 1-1 draw with Medellin.