The two sides have each navigated through two rounds of qualifying to reach this final stage, with a place in the group stage now up for grabs.
Match preview
CSKA Sofia entered Europa Conference League qualifying after finishing second in the Bulgarian top flight last season, and their journey began with a second-round tie against Makedonija.
Following a goalless draw away from home, Sasa Ilic's side took an aggregate lead through Jurgen Mattheij in the first half of the second leg and would go on to post a dominant 4-0 win as Georgi Yomov, Lazar Tufegdzic and Duckens Nazon also got on the scoresheet, booking a third-round tie with St Patrick's Athletic.
Their home leg against the Irish outfit remained goalless until the 87th minute, when Serge Atakayi put their opponents ahead, but the Reds managed to come from behind on their travels, as Mauricio Garcez and Ivan Turitsov netted goals to overturn the deficit in normal time.
Now on the back of a 1-0 win over Septemvri Sofia, thanks to Brayan Moreno's goal to stay unbeaten after five league matches and just a point off top spot with a game in hand, CSKA Sofia head into their playoff tie hoping to take a lead at home, but they face a tough test as the Swiss giants make the trip to the Vasil Levski National Stadium.
Coming into Europa Conference League qualifying on the back of a round-of-16 exit in the inaugural competition last year, and a second-placed finish in the Swiss Super League, Basel began with a second-round tie against Crusaders, and after a 2-0 home win thanks to goals from Dan Ndoye and Adam Szalai, they were able to draw 1-1 on their travels and progress with an aggregate victory.
Alexander Frei's side would then meet Brondy in the third round, and they had a hill to climb after a 1-0 away defeat in the first leg in Denmark, after Marko Divkovic hit the only goal of the game.
In a dramatic end to the first half of their home leg, Basel's initial lead, taken through Fabian Frei, was cancelled out, but Andi Zeqiri put them back in the ascendancy, and with the second half and extra time remaining goalless, the tie eventually went to a penalty shootout and the RotBlau prevailed.
On the back of that triumph, Basel's league campaign continued on Sunday with a home contest against Lugano, and after the game looked set to finish as a stalemate, their visitors snatched all three points with two goals in injury time, seeing Frei's side remain winless with just three points from their opening four outings in the Swiss top flight.
Given their tough start to the domestic season, Basel will be desperate to secure continental group-stage football again this campaign with the chance to gain an advantage with a positive result away from home.
CSKA Sofia Europa Conference League form:
CSKA Sofia form (all competitions):
Basel Europa Conference League form:
Basel form (all competitions):
Team News
CSKA Sofia have several options to choose from going forward, with the likes of Brayan Moreno and Duckens Nazon vying to feature up front.
Brusque loanee Mauricio Garcez has been their key man in attack so far this season, contributing six goals and two assists in eight appearances across league and continental action.
Amos Youga should continue to anchor the midfield, with Stanislav Shopov also expected to feature in the engine room.
Basel's line should be led by Andi Zeqiri, who netted his first goal following a loan arrival from Brighton & Hove Albion in their second-leg win over Brondby.
Hungarian veteran Adam Szalai will also be hoping for a starting berth in attack, while Dan Ndoye and Liam Millar provide threat on the wings.
Marwin Hitz will again play between the sticks following his summer arrival from Borussia Dortmund, with Kasim Adams set to partner Arnau Comas at the heart of a back four.
CSKA Sofia possible starting lineup:
Busatto; Donchev, Mattheij, Koch, De Nooijer; Garcez, Youga, Shopov, Tufegdzic; Moreno, Nazon
Basel possible starting lineup:
Hitz; Lang, Comas, Adams, Pelmard; Frei, Burger; Ndoye, Millar; Szalai, Zeqiri