Although they have an advantage, Renato Gaucho's side make the trip knowing that their work is far from done, and their lead will certainly come under fire on away turf.
Match preview
Ecuadorian champions Barcelona SC cruised through the Copa Libertadores group stage, earning 13 points from six games to top the group, before qualifying through the round of 16 with a 3-2 aggregate win over Argentinian outfit Velez Sarsfield.
Fabian Bustos's side then took on Brazilian side Fluminense, and after earning a 2-2 away draw with a late goal, and playing out a 1-1 draw on home turf, they advanced on away goals and met Flamengo.
The Idolo de madera were handed a 2-0 defeat on their travels, and will now be desperate to bounce back in the second leg and battle to reach the final.
Despite a strong run to the semi-finals, Bustos's men will not be filled with confidence by their domestic season, as they sit seventh in the second round of the Ecuadorian Serie A with four wins and three defeats from their opening seven matches.
Nonetheless, they will aim to cause a major upset and overturn the deficit on Thursday, while Flamengo arrive looking to defend their lead.
After topping their group with 12 points, before cruising past Defensa y Justicia in the round of 16, Flamengo met Paraguayan outfit Olimpia in the Copa Libertadores quarter-finals.
Renato Gaucho's men picked up a dominant 4-1 win away from home, and capped off an eye-catching two-legged performance with a 5-1 thrashing on home turf, progressing to the semi-finals in style.
In their home clash with Barcelona SC last week, Bruno Henrique hit a first-half brace to give his side a 2-0 lead, and, while the visitors were reduced to 10 men on the stroke of half time, the scoreline did not change in the second half.
That followed a disappointing defeat to Gremio in the Campeonato Brasileiro Serie A, and they were unable to build on the continental win upon their return to league action last time out, as their title hopes took another hit with a draw against strugglers America Mineiro.
The game looked set to end goalless until Michael finally hit what appeared to be the winning goal for Flamengo in the 89th minute, only for them to be pegged back by an Alexandre Egea equaliser in the 95th minute.
Now trailing league leaders Atletico Mineiro by 11 points, Gaucho should see the Copa Libertadores as his side's best chance of earning silverware this term, and they will be keen to see out the aggregate victory on Thursday and go within one game of lifting the trophy.
Barcelona SC Copa Libertadores form:
Barcelona SC form (all competitions):
Flamengo Copa Libertadores form:
Flamengo form (all competitions):
Team News
Barcelona SC come into the second leg without midfielder Nixon Molina, who will serve a suspension after his red card in the trip to Flamengo.
In their search of a big victory to overturn the aggregate deficit, Gonzalo Mastriani should lead the line again, likely with the support of the attacking trio of Damian Diaz, Adonis Preciado and Emmanuel Martinez.
Meanwhile, Carlos Garces will be pushing to return to the starting XI after a substitute appearance last time out, having registered three goals and four assists in their Copa Libertadores campaign this season.
Fernando Leon and Williams Riveros should continue their established partnership at the heart of the back four, while Sergio Lopez could operate alongside Bruno Pinatares in the engine room in the absence of Molina.
Flamengo will also face a suspension, after defender Leo Pereira was sent off in the dying minutes of the first leg.
Willian Arao and Andreas Pereira form a talented midfield duo, while Gabriel Barbosa will continue to lead the line, having registered 10 goals and four assists in 11 Brazilian top-flight games this season.
Gaucho has plenty of options to deploy in the attack behind Barbosa, with Bruno Henrique bound to keep his place after a brace in the home leg, while Vitinho, Giorgian de Arrascaeta and Everton Ribeiro will also be vying for starting spots.
Barcelona SC possible starting lineup:
Burrai; Castillo, Leon, Riveros, Pineida; Pinatares, Lopez; Garces, Diaz, Preciado; Mastriani
Flamengo possible starting lineup:
Alves; Isla, Luiz, Caio, Rene; Arao, Pereira; Ribeiro, De Arrascaeta, Henrique; Barbosa
We say: Barcelona SC 0-1 Flamengo (Flamengo win 3-0 on aggregate)
While Barcelona SC will be chasing the game, we ultimately see Flamengo having too much quality, and expect the Brazilian side to extend their lead with another win.
The visitors' abundance of talent all over the pitch makes them a daunting proposition for any side, and we see them cruising into the final.