An impressive draw away in the Italian capital got Athletic's campaign off to a good start, while AZ were victorious on matchday one.
Match preview
Bilbao will feel they are back where they belong after such a surprisingly lengthy absence from continental football, considering they qualified seven times in nine years between 2009 and 2018.
Ensuring European football came to San Mames was believed to be a deciding factor in Nico Williams staying with the club over the summer too, with the local boy keen to represent his club on the continent.
Aitor Paredes's late goal at the Stadio Olimpico saw Athletic clinch a point away to Roma on the opening matchday, in what could have been perceived as their most difficult match in the league phase.
Ernesto Valverde's men have to go to Turkey twice, but they will fancy their chances in all four home games, facing AZ, Slavia Prague, Elfsborg and Viktoria Plzen.
Athletic drew 1-1 again at the weekend, but in opposite circumstances to the Roma game, as Sevilla nicked a point in injury time, meaning Valverde saw his side drop out of the La Liga top four despite going into the game having won four of their last five league games.
Despite those dropped points, AZ will be quaking in their boots heading to San Mames knowing the kind of form Athletic produce at home, as the loss to Atletico Madrid here at the end of August is their sole defeat on home soil since the opening day of last season, which came against Real Madrid on that occasion.
The Dutch side will also come into this encounter slightly bruised after seeing their unbeaten start to the season end at the weekend.
Maarten Martens's side had taken 19 points from a possible 21 in the league, but were beaten 2-1 at home to Utrecht, allowing PSV Eindhoven the opportunity to pull further clear at the top of the Eredivisie.
They at least got off to a winning start in this competition, coming from behind to defeat Elfsborg 3-2, with Troy Parrott netting the winner from the penalty spot after Ruben van Bommel had bagged a brace.
That was just a third Europa League win in 11 outings for AZ though, and their away form in Europe is a worry, having lost five in a row on the road, and on their last three trips to Spain.
While a repeat of their heroics from 1981 when the Alkmaar club reached the final are unlikely, replicating a similar journey they had on the way to the Europa Conference League semi-finals in 2023 would be appreciated.
Athletic Bilbao Europa League form:
D
Athletic Bilbao form (all competitions):
L
W
W
W
D
D
AZ Alkmaar Europa League form:
W
AZ Alkmaar form (all competitions):
D
W
W
W
W
L
Team News
Athletic's Spanish international goalkeeper Unai Simon remains out with a wrist injury and is not expected to return until after the upcoming break.
That may provide a problem domestically, as backup keeper Julen Agirrezabala was sent off at the weekend, but he will be available here before serving a La Liga suspension.
Yeray's hamstring injury will keep him sidelined, and Oihan Sancet is missing up front, while the experienced Ander Herrera is also nursing a muscular problem at present.
AZ's Bruno Martins Indi was injured and suspended for their opener against Elfsborg, but returned at the weekend and is set to start again here.
After a four-goal salvo against Heerenveen recently, ex-Tottenham Hotspur man Parrott has scored in back-to-back games against Elfsborg and Utrecht, and should lead the line again.
Wouter Goes is not yet ready to return from injury, while backup keeper Sem Westerveld is also currently out with a knee issue.
Athletic Bilbao possible starting lineup:
Agirrezabala; Gorosabel, Dani Vivian, Paredes, Yuri Berchiche; Vesga, Ruiz de Galarreta, Unai Gomez; I Williams, Guruzeta, N Williams
AZ Alkmaar possible starting lineup:
Owusu-Oduro; Maikuma, Penetra, Martins Indi, Wolfe; Clasie, Mijnans, Koopmeiners; Sadiq, Parrott, Van Bommel
We say: Athletic Bilbao 2-0 AZ Alkmaar
Athletic rarely slip up at home, and after an impressive result against Roma, they could be very competitive in the Europa League this season.