The winners of this contest will advance to the second round where they will be joined by 55 other clubs ahead of next month's draw.
Match preview
Since securing promotion from the Spanish second tier, Espanyol have endured a difficult start to life back in the top flight having lost seven of their opening 11 La Liga matches this term.
Los Periquitos have suffered defeat in five of their last six league games, including last weekend's 2-0 loss at home to Sevilla, and they currently sit 17th in the table, hovering just above the relegation zone by one point.
Manolo Gonzalez has acknowledged that his Espanyol side are paying the price for making several mistakes and he is determined to see his team return to winning ways in midweek, before they prepare for a daunting away encounter with La Liga leaders and Catalan rivals Barcelona on Sunday.
Espanyol, who celebrated their 124th anniversary on Monday, are yet to win away from home so far this season (D1 L4), but they have a strong record in the first round of the Copa del Rey, progressing in each of the last 21 seasons since losing 1-0 at Alicante back in 2002.
Los Periquitos will be regarded as firm favourites to come out on top against Thursday's opponents San Tirso, who are one of the lowest-ranked teams in this season's Copa del Rey.
The Mabegondo-based club won the Copa de A Coruna, Copa Diputacion and Supercopa de Galicia last season and they have since progressed to the first round proper of this year's Copa del Rey after beating Selaya 5-3 on penalties in the preliminary round, following a 1-1 draw in normal time.
Head coach Fabio Rodriguez admitted after that match that he broke down in tears after his side secured their place in the first round, and he is excited to see how his players will step up for the challenge against La Liga opposition on Thursday.
Since their penalty-shootout triumph with Selaya on October 9, San Tirso have picked up four points across three league games in Preferente de Galicia - Group 1, most recently winning 2-0 at home to Mino last weekend to help them climb up to eighth in the standings.
San Tirso Copa del Rey form:
San Tirso form (all competitions):
Espanyol form (all competitions):
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Team News
San Tirso are expected to name their strongest possible starting lineup for this crunch match, and it will likely include winger Cristian Quintans who scored in the previous round.
The likes of Denis, Pedro Carpente, Rey Diaz, Paulo Vigo and Adrian Suarez, who have all been first-team regular this season, are also set to be named in the first XI.
As for Espanyol, they are set to be without Fernando Calero (muscle), Eduardo Exposito (knee), Jose Gragera (thigh) and Naci Unuvar (unspecified) due to injury.
Javi Puado recovered from a knee injury to play for 81 minutes against Sevilla last weekend, but it remains to be seen whether he will be involved on Thursday, while a number of other first-team stars including Marash Kumbulla, Carlos Romero, Alex Kral, Alejo Veliz and Jofre Carreras could also be rested.
San Tirso possible starting lineup:
Adri; Rellan, Lago, Pablo Vigo, Gamallo; Rey; Xian, Meijide, Quintas; Harvest, Denis
Espanyol possible starting lineup:
Pacheco; Jurado, Cabrera, Luis Catala, Hinojo; Smith, Bauza; Roca, Carvalho, Almansa; Mingo
We say: San Tirso 0-3 Espanyol
If Espanyol are to name a strong side with several first-team players, then you would expect the La Liga team to cruise to a comfortable victory. Even if the visitors were to hand some of their B team youngsters a run-out in this one, they should still have enough quality to prevail against their non-league counterparts.