Pascal Jansen's side dished out a 4-0 thrashing in the home leg and find themselves one game away from the group stage.
Match preview
Following a commendable fifth-placed finish in the Primeira Liga last season, Gil Vicente entered Europa Conference League qualifying in the third round and met Riga FC.
A 1-1 draw away from home was followed by a dominant 4-0 win in the second leg to see Ivo Vieira's side progress to the playoff round, as Fran Navarro netted a brace after they went ahead through an Ngonda Muzinga own goal and a Kevin Villodres finish.
Ahead of their trip to Netherlands for the first leg against AZ Alkmaar last week, Os Gilistas suffered a disappointing 1-0 defeat at the hands of Arouca, and they would not be able to turn their form around, being on the wrong end of a 4-0 thrashing on that occasion.
Now with a major hill to climb if they are to progress to the group stage, and on the back of a goalless draw with a Famalicao in the third round of league fixtures, Gil Vicente will look to upset the odds and overturn the four-goal deficit on Thursday.
Their visitors make the trip aiming to complete the job they started last Thursday, following a rampant away display.
AZ Alkmaar have already navigated through two rounds of qualifying in their bid to reach Europe's tertiary competition for the second straight season, firstly seeing off Tuzla City with a 5-0 aggregate win.
Pascal Jansen's side then met Dundee United, and, after a 1-0 defeat in Scotland, they turned the game on its head in eye-catching fashion, recording a 7-0 thrashing on home turf with Vangelis Pavlidis and Tijjani Reijnders helping themselves to first-half braces before Hakon Evjen, Dani de Wit and Mayckel Lahdo added goals.
The Kaaskoppen went into last week's contest in Alkmaar following a hard-fought 3-2 away win over Sparta Rotterdam, and they would take a 1-0 lead into the final 15 minutes thanks to Dani de Wit's goal, before all but securing their advancement as Lahdo, Pavlidis and Mees de Wit got on the scoresheet to make it 4-0 at the halfway stage of the tie.
They will now look to cruise through to the group stage with momentum and stretch their aggregate lead on the night.
Gil Vicente Europa Conference League form:
Gil Vicente form (all competitions):
AZ Alkmaar Europa Conference League form:
AZ Alkmaar form (all competitions):
Team News
In the continued absence of first-choice goalkeeper Stanislav Kritsyuk, 21-year-old Brazilian stopper Andrew will continue to play in the Gil Vicente goal.
Vieira should call back on striker Fran Navarro, who was dropped to the bench for last week's first leg despite hitting a brace in their 4-0 beating of Riga, while summer signing Ali Alipour could also keep his place in attack, given their need for goals.
Kanya Fujimoto will continue to offer support going forward from midfield, while a change in shape could see Giorgi Aburjania sacrificed for more attacking players like Kevin Villodres and Juan Manuel Boselli.
Coming in with a big lead, AZ Alkmaar make take the opportunity to rest a few key players with an Eredivisie contest with Cambuur looming, and, as a result, we may not see the likes of Vangelis Pavlidis and Dani de Wit from the outset after both added to their goal tallies in the first leg.
Instead, Yusuf Barasi may lead the line with support from Mayckel Lahdo, with Fedde de Jong and Peer Koopmeiners candidates to come into the midfield.
Further back, captain and key centre-back Bruno Martins Indi should still be deployed to ensure they get over the line, while Mees de Wit could come in in place of Milos Kerkez on the left-hand side of the back four after his goal last week.
Gil Vicente possible starting lineup:
Andrew; Veiga, Fernandes, Araujo, Gomes; Carvalho, Fujimoto; Boselli, Villodres; Alipour, Navarro
AZ Alkmaar possible starting lineup:
Verhulst; Sugawara, Martins Indi, Beukema, M De Wit; Koopmeiners, Reijnders; Evjen, De Jong, Lahdo; Barasi