Atlas, who finished bottom of the standings in the Apertura championship won by Monterrey in December, continued their fine start with a third victory, 1-0 away to promoted Necaxa on Friday.
Shaven-headed Chile striker Humberto "Lollipop" Suazo scored after two minutes to hand Monterrey their first points after two defeats with Mario Ortiz missing a 53rd-minute penalty and the chance to salvage a draw for Atlante.
Cruz Azul, favourites to win the Apertura championship in December before their shock quarter-final elimination by Pumas, took a 2-0 half-time lead at their Azul ground in the capital.
Argentine striker Emanuel Villa opened the scoring and right-back Horacio Cervantes made it two with a shot from outside the box which took a deflection on defender Marco Antonio Palacios.
Pumas hit back with three goals in 20 minutes, two from forward Juan Cacho either side of veteran Paraguayan defender Dario Veron's headed equaliser from Brazilian-born Mexican Leandro Augusto's cross.
Chilean midfielder Hugo Droguett salvaged a point for Cruz Azul, whose tally is four from three matches, when he pulled them level eight minutes from time with a left-footed shot after a one-two with substitute Cesar Villaluz.
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