Two-time competition winners IFK Gothenburg visit Fola Esch hoping to avoid a surprise UEFA Europa League elimination on Thursday.
Gothenburg - winners of the then-UEFA Cup in 1982 and 1987 - were held to a goalless draw in last week's opening leg of the first-round qualifier.
And that has heaped the pressure on Mikael Stahre's men, who travel to Luxembourg needing a positive result.
Tromso should have no such worries after hammering Estonia's Tartu Santos 7-0 on the road in their first leg.
Another side from Norway - Rosenborg - won well last week, as a 4-0 triumph against Latvia's Jelgava gives them one foot in the second round, despite the upcoming away trip.
Aberdeen will also hit the road in good spirits. They beat Daugava Riga 5-0 in last week's first leg at Pittodrie.
There was treble joy for Kazakhstan in the first legs, and Astana, Shakhter Karagandy and Kairat all hold the advantage heading into return clashes against Pyunik, Shirak and Kukesi.
Koper are another side virtually in the second round already. They host Celik with a 5-0 lead already in the bag.
Cukaricki, Stjarnan and Botev Plovdiv will be buoyant with 4-0 leads against Sant Julia, Bangor City and Libertas respectively, while FH are three goals to the good against Glenavon, as are Metalurg Skopje when they meet Moldova's Santa Coloma, and Vaduz over Gibraltan side College Europa.
Northern Irish sides also completed a hat-trick of wins last week.
Crusaders beat Ekranas of Lithuania 3-1 to give themselves a healthy lead while Derry City will prepare for their trip to Aberystwyth Town positive of progression. They won 4-0 in the first leg.
But Linfield may not be as confident, with Michael Carvill's late strike needed to give them all three points in a 2-1 win against B36 of the Faroe Islands.
Siroki Brijeg, Spartak Trnava, RNK Split and Dundalk all hold two-goal leads and should progress.
Skendija 79, Sillamae Kalev, VPS, Vikingur, Buducnost and Diosgyor all head into their second legs - against Zimbru, Honka, Brommapojkarna, Daugava Daugavpils, Folgore/Falciano and Birkirkara respectively - leading 2-1.
A further six sides hold one-goal advantages, with MYPA joined by Chikhura, Inter Baku, Flamurtati Vlore, Differdange and Nomme Kalju in holding slender leads.
Three ties are firmly in the balance after goalless first legs, with Veris and Litex Lovech, Banga and Sligo Rovers, and Lovcen and Zeljeznicar all hoping to find the back of the net.
Other sides who were unable to be separated were Sliema Wanderers and Ferencvaros, Airbus UK and Haugesund, and Laci and Rudar, setting up exciting second-leg clashes.