A Copa del Rey triumph saw the Seville outfit guarantee a place in the group while their hosts fought through qualifying to reach this stage.
Match preview
After triumphing for the 31st time in the Finnish top flight last season, HJK Helsinki entered Champions League qualifying in the first round and got past Rigas Futbola Skola on a penalty shootout before meeting Viktoria Plzen in a second-round tie.
They only suffered a narrow 2-1 defeat on home soil but would see their opponents run away with the game in the away leg, eventually dishing out a 5-0 thrashing and forcing the Klubi into qualifying for Europe's secondary competition.
On their entry to Europa League action, Toni Koskela's side met Maribor and prevailed with a 3-0 aggregate victory, firstly winning 2-0 away from home before Santeri Hostikka hit the only goal in Finland, booking a playoff tie with Silkeborg as a result.
David Browne gave them a one-goal lead going into the away leg of that tie, and the Klubi were able to hold on and progress to the group stage as they drew 1-1 in Denmark, thanks to Malik Abubakari's opener.
They now head into the group stage having strengthened their position at the summit of their domestic top flight with a narrow wins over SJK and VPS, moving two points clear in top spot after 21 league outings, and they will look to take an impressive scalp against the visiting Spanish side to put three points on the board in the Europa League on Thursday.
Real Betis will make the trip for their first continental game of the season, having bypassed qualifying thanks to their cup triumph last season.
Manuel Pellegrini's side eventually finished fifth in La Liga, but their campaign was marked by a Copa del Rey run, in which they reached the final with wins over Alicante, Talavera, Real Valladolid and later Sevilla, Real Sociedad and Rayo Vallecano.
That booked them a contest with Valencia in the final in Seville, and Borja Iglesias opened the scoring only for the visitors to draw level on the half-hour mark, before the tie went to a penalty shooutout with no further goals and Los Verdiblancos prevailed as Willian Jose, Joaquin Andres Guardado, Cristian Tello and Juan Miranda all converted their spot kicks.
Heading towards the new term after securing silverware for the first time since 2015, Pellegrini's men made an impressive start, winning their first three La Liga games against Elche, Mallorca and Osasuna.
That perfect record was put to an end last time out by defending champions Real Madrid, as Sergio Canales's equaliser was followed by a Rodrygo winner for Los Blancos, and Real Betis will now look to bounce back and put their first points of the group stage on the board with an away win on Thursday.
HJK Helsinki Europa League form:
HJK Helsinki form (all competitions):
Real Betis form (all competitions):
Team News
HJK Helsinki will remain without important attacker Roope Riski, who has been out of action with a knee injury since mid-June.
In his absence, Malik Abubakari could again lead the line, while Santeri Hostikka should come back in from the outset after netting the winning goal off the bench in their league win over VPS last time out.
David Browne is another threat from out wide in a wing-back role, with the Klubi again set to line up in a 3-4-3 shape with Santeri Vaananen and Lucas Lingman operating in the engine room.
We are yet to see whether Pellegrini will prioritise Real Betis' Europa League campaign alongside La Liga, but they should still travel with a strong squad even if rotations are made to the team that fell to Real Madrid.
Centre-back German Pezzella will return to contention after serving a suspension last time out and could come straight back in, while Martin Montoya and Luiz Felipe may also play in the defence with Andres Guardado set to keep his place alongside Guido Rodriguez at the base of midfield.
Further forward, Willian Jose could be given a chance to lead the line if Borja Iglesias and Nabil Fekir are rested, while veteran Joaquin is also likely to come back into the starting XI on the right wing.
HJK Helsinki possible starting lineup:
Hazard; Raitala, Hoskonen, Halme; Browne, Lingman, Vaananen, Murilo; Hostikka, Abubakari, Tanaka
Real Betis possible starting lineup:
Silva; Montoya, Felipe, Pezzella, Moreno; Rodriguez, Guardado; Joaquin, Rodri, Canales; Jose