The Montreal Impact got the job done with a 2-0 win at home, but now comes the hard part.

Ignacio Piatti and Victor Cabrera scored in the first half as the Impact posted a an impressive 2-0 victory over Alajuelense in the first leg of their CONCACAF Champions League semifinal on Wednesday night.

But it will likely be much tougher in the second leg of the two games, aggregate goals series on April 7 in Alajuela, Costa Rica, even if Montreal goes in with a two-goal lead.

"Costa Rica is not going to be easy," said captain Patrice Bernier, who got a huge ovation from the 33,675 at the domed Olympic Stadium when he went in as a second half substitute. "There'll be the crowd, the turf.

"The referees have a tendency to get influenced there, so we have to be sharp and alert. Certain fouls sometimes don't go your way and you're down one man and you've got to be careful. But we've got a lot of experience on this team."

The two legs of a CONCACAF series can be vastly different.

In the quarter-finals, Alajuelense wiped out D.C. United 5-2 at home before wrapping up the series 6-4 in Washington.

And the Impact had their own nightmare in 2009 when they won the first leg of a quarter-final 2-0 at home, only to go to pieces late in the second match, despite taking an early lead, and losing 5-4 on aggregate in Mexico.

But midfielder Nigel Reo-Coker was impressed enough with the Impact's solid two-way game that he felt they should be able to wrap it up and become only the fifth Major League Soccer team to reach the CONCACAF final.

"We put ourselves in a great position," said Reo-Coker. "If you look at our performance, we've got to be very confident when we go there.

"We have to have the same mental approach, the same commitment as a team and the same work rate."

The Impact jumped on Alajuelense early, scoring twice in the first 14 minutes, and could have had more in a one-way first half.

Alajuelense had more pressure in the second half, but the defence led by centrebacks Bakary Soumare and Laurent Ciman, and strong game from goalie Evan Bush, allowed few dangerous chances.

Coach Oscar Ramirez said his Alajuelense team adjusted after the early goals and had the better of the play the rest of the way. He expects it to be very different in his team's tight 17,895-seat stadium.

"We think we did our best and we will do the same in Costa Rica," he said through an interpreter. "Maybe we will have one of those magic nights when the Costa Ricans are playing in their typical style.

"But we know we're playing a good team that does a great job defending."

In the other semifinal, Herediano downed the tournament favourite America of Mexico 3-0 in the first leg in Costa Rica on Tuesday.

The Impact have an MLS match Saturday at New England.