Inter Milan were held to a 1-1 draw at home by Bologna in Serie A on Sunday after a fine volley from Ivan Perisic.
Mauro Icardi inspired a superb comeback win for Inter as they beat Juventus 2-1 on Sunday, while Roma lost at Fiorentina.
Gonzalo Higuain starred for Juventus with two goals as they beat Sassuolo 3-1 in Serie A on Saturday, as Napoli won 3-0 at Palermo.
Man Utd will face Fenerbahce, Feyenoord and Zorya Luhansk in the Europa League, while Southampton are in a group with Inter Milan.
Inter Milan suffered a surprise 2-0 defeat to Chievo on the opening weekend of Serie A while Napoli also struggled.
Francesco Totti made his 600th Serie A appearance as Roma moved up to second spot with a 3-0 win over Chievo.