How Europa League play-offs work and what happens to Man Utd vs Barcelona winner

manchestereveningnews.co.uk:

Manchester United welcome Barcelona to Old Trafford for the first time in almost four years as the Europa League knockout round play-off concludes on Thursday.

The tie between two former Champions League winners is one of seven that remains finely poised ahead of the return leg taking place.

Perennial champions of UEFA's second-tier competition, Sevilla, are the only side that seems assured of success by taking a 3-0 aggregate lead over PSV Eindhoven into their second leg.

European giants Ajax, Juventus and Sporting all drew their first legs against Union Berlin, Midtjylland and Nantes, respectively, while three other sides (Monaco, Roma and Shakhtar Donetsk) only won their initial encounters by a one-goal margin, but what happens to the sides that do come out on top in their play-off ties? READ MORE: When is Europa League last 16 draw?