Cruz Azul will take the narrowest of advantages into the second leg of the Clausura final after they claimed a 1-0 home win over Mexico City rivals Club America.
The hosts, who finished fifth -- three places below their opponents -- in the table, scored the only goal of the game through Christian Gimenez in the 19th minute.
America will attempt to overturn the deficit at the Azteca on Sunday.
"We have an advantage over a great rival," Gimenez said. "They played well and improved in the second half and we shot back, but the concentration and teamwork worked for us. America is a complicated foe and earned a spot in the final and we will try to stay ahead."