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.