Runners-up in the Clausura last season, Cruz Azul should be among the contenders once again and recorded a 1-0 win at home against Monterrey.
Rogelio Chavez's 53rd-minute penalty was the difference between the teams at Estadio Azul, where the hosts finished with 10 men after Gerardo Torrado was sent off.
Cruz Azul missed a first-half penalty but converted their second chance from the spot, with Chavez sending Juan Ibarra the wrong way.
Toluca, 10-time league champions, were beaten in their opening game on Sunday, suffering a 1-0 loss at home to Pachuca.
Othoniel Arce's well-placed 79th-minute effort found the bottom corner to give Pachuca the three points.
Morelia are top of the table after their 3-1 win at newly promoted Queretaro.
Edgar Andrade opened the scoring with a simple finish in the 28th minute before they made it 2-0 early in the second half.
Jefferson Montero struck, beating a defender before delightfully chipping goalkeeper Edgar Hernandez and Hector Mancilla wrapped up all three points in the 73rd minute.
Mario Osuna netted a consolation goal for the hosts with two minutes remaining.
Elsewhere, a Dario Benedetto hat-trick was not enough for Tijuana, who played out a 3-3 draw at home to Atlas.
Benedetto struck twice in the first 18 minutes and again just after the hour-mark but his side gave up a 3-1 lead.
Angel Reyna's late goal saw Veracruz draw 2-2 at home to Chiapas, Leon edged Atlante 1-0 and Puebla and Pumas UNAM played out a 1-1 draw.
‘Diaz is often our most dangerous guy for the full 90 minutes, every time I’ve seen him’: Liverpool legend makes shock claim about the Reds' attack
“Marcus Rashford will always be under scrutiny, he can’t just ask people to shut up, they won’t. He has to show he’s obsessed with football again, the best train more than anybody’: former Manchester United striker issues warning to Old Trafford star
