The winners of the tie will face either Atletico Goianiense or Sao Paulo in the grand finale of South America's secondary club tournament.
Match preview
Independiente del Valle suffered a first defeat across all competitions since July as they were beaten 2-1 by Universidad Catolica on Sunday.
Martin Anselmi's men went behind to Ismael Diaz's opener midway through the first half before conceding 30 minutes into the second half to the aforementioned Diaz, rendering Junior Sornoza's last strike inconsequential.
Consequently, Los Negriazules have dropped down to second place in the Liga Pro standings, two points adrift of current leaders SD Aucas.
Next up for the Ecuadorian champions is the penultimate step towards securing a second-ever Copa Sudamericana final having gone all the way in the 2019 edition.
Unbeaten in seven of their last eight matches on home turf in which they have picked up six victories, Thursday's hosts will be aiming to edge ahead in the tie ahead of next week's return leg.
Melgar made it five league wins in a row as they saw off the threat of Universidad San Martin at Estadio Monumental Virgen de Chapi on Saturday.
Pablo Lavallen's men took control of the contest with quickfire second-half goals from Jean Archimbaud and Martin Perez after which Josue Rodriguez pulled one back late on.
Consequently, Los Rojinegros have moved up to second place in the Liga 1 and are now just two points behind Atletico Grau with two games in hand.
Off the back of a seven-game unbeaten run on the road which includes five victories and seven clean sheets, Thursday's visitors will make the journey to Quito with the wind in their sails.
Independiente del Valle Copa Sudamericana form:
Independiente del Valle form (all competitions):
Melgar Copa Sudamericana form:
Melgar form (all competitions):
Team News
Junior Sornoza was on target for Independiente del Valle in the last edition of this fixture and he will be looking to deliver the goods once again.
Lautaro Diaz had to make do with a second-half cameo last time out but the midfielder is expected to return to the starting XI for this one.
Bernardo Cuesta has been directly involved in 10 goals in his 11 Copa Sudamericana games this term, making the Argentinian one to keep an eye on.
Thirty-year-old Cristian Bordacahar is yet to feature in any of his side's most recent three games and he is expected to miss Thursday's contest.
Independiente del Valle possible starting lineup:
Ramirez; Ortiz, Carabajal, Chavez; Vargas, Gaibor, Diaz, Cabezas; Mercado, Minda, Ayovi
Melgar possible starting lineup:
Caceda; Lazo, Deneumostier, Lujan, Reyna; Archimbaud, Tandazo, Perez; Cuesta, Vidales, Quevedo