While the Dutch side slipped up spectacularly against Zrinjski Mostar in Bosnia, Legia slayed group favourites Aston Villa to get off to a perfect start.
Match preview
Building on last term's fourth-placed finish, AZ have won all but one of their domestic fixtures this season, and after dropping points for the first time last Thursday, the Alkmaar club eased to a comfortable victory against Fortuna Sittard at the weekend.
A 4-0 home win moved Pascal Jansen's men back within two points of leaders PSV Eindhoven. Sitting second, with 19 points on the board from seven league games, their 2023-24 campaign currently promises to be a memorable one.
However, their one failure so far came in a remarkable Europa Conference League defeat away to Zrinjski Mostar - the first Bosnian club to feature in any UEFA competition group stage.
The circumstances of AZ's reverse will have been all the more concerning for Jansen, who watched on as his team blew a 3-0 half-time lead, frittering away their advantage within 26 second-half minutes to lose 4-3 at Stadion Bijeli Brijeg.
This year, Jansen - recently linked with the vacant Rangers job - is aiming to build on reaching last season's Conference League semi-finals, from which AZ were eliminated by eventual winners West Ham United. Any more capitulations like in this term's opener, though, would soon put paid to that.
By contrast with their hosts, Legia Warsaw enjoyed a dream debut on matchday one, as after coming through three qualifying rounds during the summer they stunned Aston Villa in their first Group E fixture.
Four of the goals in a five-goal contest came during the first half at Stadion Wojska Polskiego, as Legia took the lead three times and then finally managed to hold on to it after Ernest Muci's decisive strike shortly after the break.
Pawel Wszolek had opened the scoring after only three minutes, and after plenty of twists and turns, Poland's most successful club eventually came out on top against expensively-assembled Premier League opponents.
To reach this stage, Legia overcame Ordabasy, Austria Vienna and Midtjylland in spite of conceding 13 goals and needing a penalty shootout to beat the latter in a playoff, so coach Kosta Runjaic has hardly had chance to draw breath during his club's eventful European run to date.
Meanwhile, in the Ekstraklasa - where Legia are aiming to win the title for the first time since 2021 - Runjaic's side tasted defeat for the first time on Sunday, with a 2-0 loss to Jagiellonia following six wins and two draws.
Nonetheless, despite failing to score for the first time since mid-July, the Legionnaires should remain in good spirits ahead of their trip to Alkmaar, where they will aim to upset the odds once again.
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Legia Warsaw Europa Conference League form:
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Team News
After Riechedly Bazoer was withdrawn from last week's draw with Heracles, the AZ defender was ruled out of weekend action and could miss out again on Thursday. Bruno Martins Indi - a 36-time Netherlands international, recently returned from long-term injury - will therefore battle it out with teenager Wouter Goes to deputise in central defence.
Featuring at the heart of a 4-2-3-1 formation, Jordy Clasie and Sven Mijnans should join forces in midfield, while Dani de Wit plays a more advanced role, having contributed four league goals so far this season.
Vangelis Pavlidis starts up front, with an Eredivisie-high tally of nine goals to his name from just seven appearances - also scoring in each of the last seven domestic matches in a row.
Although Spanish striker Marc Gual started against Aston Villa last month, Legia Warsaw should turn to ex-Tottenham reserve Tomas Pekhart to lead their line this week: the 34-year-old has just been called up to the Czech Republic squad for the upcoming Euro 2024 qualifiers, having netted 10 times in all competitions this season.
Following his brace versus Villa, Ernest Muci is set to join club captain Josue in supporting the visitors' main forward.
Meanwhile, Poland international Artur Jedrzejczyk returns from an Ekstraklasa suspension; while Marco Burch was sent off in Bialystok at the weekend, but his subsequent suspension only applies to Polish competitions.
AZ Alkmaar possible starting lineup:
Ryan; Suganawa, Penetra, Martins Indi, Wolfe; Mijnans, Clasie; Lahdo, De Wit, Van Brederode; Pavlidis
Legia Warsaw possible starting lineup:
Tobiasz; Ribeiro, Jedrzejczyk, Pankov; Wszolek, Elitim, Slisz, Kun; Josue, Pekhart, Muci