Chelsea won the competition back in 2013, with Rafa Benitez in charge, beating Benfica 2-1 in the Amsterdam Arena.
Full Europa League draw:
Group A: Bayer Leverkusen, Ludogorets, FC Zurich, AEK Larnaca.
Group B: FC Salzburg, Celtic, RB Leipzig, Rosenborg.
Group C: Zenit St Petersburg, FC Copenhagen, Bordeaux, Slavia Prague.
Group D: Anderlecht, Fenerbahce, Dinamo Zagreb, Spartak Trnava.
Group E: Arsenal, Sporting CP, Qarabag, FC Vorskla.
Group F: Olympiakos, AC Milan, Real Betis, Dudelange.
Group G: Villarreal, Rapid Vienna, Spartak Moscow, Rangers.
Group H: Lazio, Marseille, Eintracht Frankfurt, Apollon
Group I: Besiktas, Genk, Malmo, Sarpsborg.
Group J: Sevilla, Krasnodar, Standard Liege, Akhisarspor.
Group K: Dynamo Kiev, Astana, Rennes, Jablonec.
Group L: Chelsea, PAOK, BATE, Vidi FC