Leones return to Mexican League finals
Rivera (2-2) allowed four hits and a walk with six strikeouts as the Leones took the best-of-7 semifinal series, 4-1.
Jose Vargas gave up two hits in the ninth, but escaped with his second save when left fielder Quincy Foster nailed Christian Herrera at the plate for the final out.
Alcantara led off the bottom of the seventh by blasting a 3-2 offering from Mexico starter Orlando Lara (3-1) over the left-field wall for his third postseason homer.
Lara surrendered a run on four hits and three walks while fanning five over six-plus frames.
Carlos Valencia's fourth-inning double for the Diablos Rojos was the game's only other extra-base hit.
Yucatan will shoot for its second straight title when it takes on the Sultanes de Monterrey in the finals.
Zack Hample is a contributor to MLB.com.