At least one former winner must fall in the preliminary rounds for the Champions League after Benfica and PSV Eindhoven were potentially paired in Monday’s playoff draw.
The match-ups for the final 12-team qualifying round were drawn before the teams had played the preceding third qualifying round, meaning all but one of the ties has four potential teams.
Salzburg and Brondby, the two teams to join the competition at this stage, were drawn together.
The makeup of the other five pairings will be settled in two-leg ties which start on Tuesday and Wednesday.
Benfica, who have appeared in seven finals in the competition winning two, must overcome Spartak Moscow to advance while 1988 winners PSV face Midtjylland of Denmark.
Three former finalists were also in the draw.
If Monaco manage to eliminate Sparta Prague they must then beat Genk or Shakhtar Donetsk to return to the group stage.
Malmo, who face former Cup Winners Cup winners Rangers in the third round, would then face Bulgarians Ludogorets or Greeks Olympiacos.
If Red Star Belgrade beat Sheriff of Moldova they would face old Croatian rivals Dinamo Zagreb or Legia Warsaw.
The six winners will advance to the group stage while losers will drop down to the Europa League.
Champions League play-off draw, first legs Aug 17-18 August, second legs Aug 24-25:
Salzburg (AUT) v Brondby (DEN), CFR Cluj (ROM) or Young Boys (SUI) v Ferencvaros (HUN) or Slavia Prague (CZE), Malmo (SWE) or Rangers (SCO) v Olympiakos (GRE) or Ludogorets (BUL), Red Star Belgrade (SRB) or Sheriff Tiraspol (MDA) v Dinamo Zagreb (CRO) or Legia Warsaw (POL), Monaco or Sparta Prague (CZE) v Genk (BEL) or Shakhtar Donetsk (UKR), Spartak Moscow (RUS) or Benfica (POR) v PSV Eindhoven (NED) or FC Midtjylland (DEN)