While Alajuelense and arch-rivals Deportivo Saprissa met in the 2004 final of the CONCACAF Champions Cup, Mexico's dominance of the six editions of the Champions League has ensured no Costa Rican club has reached the competition's decider since 2008.
Herediano have not qualified for the final in either format and will be aiming to make history when they host America on Tuesday.
Cristian Lagos was the hero for Herediano in their 3-1 quarter-final aggregate triumph over Honduras' Olimpia, scoring in both legs.
The 30-year-old striker's goal in the 2-0 away win on March 5 made it five straight matches that Lagos had scored in but he has failed to hit the back of the net in Herediano's past two league fixtures.
In the six Champions League finals, 11 of the 12 finalists have been from Liga MX but America - five-times champions in the previous format - have not been one of them and they will be desperate to change that over two legs versus Herediano.
Alajuelense will travel to Montreal on Wednesday for their semi-final first leg after they prevailed 6-4 on aggregate in the quarter-finals against another MLS club - DC United.
Last season's semi-finalists beat DC 5-2 at home and then lost 2-1 in the United States to reach the last-four.
The Impact will be looking to become the first Canadian club to qualify for a final in both the Champions League and Champions Cup eras, while no MLS outfit has won since the new format was introduced in the 2008-09 season.
Montreal coach Frank Klopas is unsure what to do with his midfield against Alajuelense, with right-winger Justin Mapp out for four months with an elbow injury.
Klopas generally plays with Mapp and Dilly Duka as inverted wingers in a 4-2-3-1 but may switch tactics due to the former's absence.
"If you put Dom [Oduro] out there [on the right], you've got to play a little different, it depends," Klopas said.
"If a team plays higher on the pitch, you can use him because of his pace. [Maxime] Tissot, he's going to come in, but he actually has a very good service and he provides a little more width on the field – he's not one of those guys that comes inside as much as Justin or Dilly."
