Frank de Boer's Ajax Amsterdam are unbeaten in their past 17 competitive matches, dating back to November last year.
Ahead of welcoming the Austrians to Amsterdam Arena for the first leg of their round-of-32 tie, Ajax thrashed Heerenveen 3-0 in the Eredivisie, which they lead by four points.
Lasse Schone struck a hat-trick in that win – including two goals from the penalty spot – as Ajax continued their impressive form.
With Davy Klaassen, Kolbeinn Sigporsson, Schone and Siem de Jong, De Boer's men have the quality to go deep in the Europa League.
Salzburg are also in impressive form ahead of the first leg, on a nine-match winning run and 17 points clear atop the Bundesliga.
The strike partnership of Brazilian Alan (18 goals) and Spaniard Soriano (17) has been the key to Salzburg's success.
Elsewhere on Thursday, Portuguese giants Porto host mid-table Bundesliga outfit Eintracht Frankfurt at the Estadio Do Dragao.
Porto, second to Benfica in Liga Sagres, are favourites to progress against an Eintracht side struggling in the German top flight.
Benfica, last year's runners-up, travel to Thessaloniki in what will be a tricky first leg against the Greece Super League's second-placed side PAOK.
Rafael Benitez's Napoli travel to meet Premier League side Swansea, while Serie A leaders Juventus host Trabzonspor in Turin.
Tottenham travel to Ukraine to face Dnipro Dnipropetrovsk, while Russian Premier League strugglers Anzhi host Genk in Ramenskoye.
Mid-table Serie A side Lazio host Bulgarian league leaders Ludogorets in Rome and Czech outfit Viktoria Plzen take on Shakhtar Donetsk.
Sevilla enter their clash against Maribor in Slovenia on the back of a six-game winless run, while relegation-threatened La Liga side Real Betis host Rubin Kazan.
Swiss Super League leaders Basel face the tricky trip to Israel to meet table-topping locals Maccabi Tel Aviv at Bloomfield Stadium.
AZ Alkmaar visit Slovan Liberec, Dynamo Kyiv host Valencia, Fiorentina travel to Danish strugglers Esbjerg and Chornomorets take on Lyon.
