The 40 teams who qualified on Thursday have been divided into five seeding pools of eight with a team from each pool going into the eight groups of five when the draw is made in Switzerland.
Teams from the same country will be separated.
Each club play two matches at home and two away in the group stage.
The winners, runners-up and third-placed sides advance to the last 32 where they will be joined by the eight third-placed clubs from the Champions League group stage. The competition then becomes two-legged knockout again.
The final takes place on May 18 at the Jose Alvalade Stadium, home of Sporting Lisbon, who are in the second pot of seeds.
Pot 1 - Lazio, Parma, Feyenoord, Newcastle, AEK Athens, Stuttgart, Bruges, Rangers.
Pot 2 - Villarreal, Auxerre, Schalke, Sporting, Real Zaragoza, Besiktas, Benfica, Lille.
Pot 3 - Athletic Bilbao, Sevilla, Dinamo Zagreb, Basel, Sochaux, Middlesbrough, Utrecht, Graz AK.
Pot 4 - Partizan Belgrade, Steaua Bucharest, Hearts, Heerenveen, Alemannia Aachen, Amica Wronki, Panionios, Dnipro Dnipropetrovsk.
Pot 5 - Ferencvaros, Standard Liege, Egaleo, AZ Alkmaar, Zenit St. Petersburg, Beveren, Austria Vienna, Dinamo Tbilisi.