Cristiano Ronaldo's Manchester United have been drawn against Barcelona in the Europa League knockout round play-offs, and Twitter has erupted.The Red Devils could only finish second in Group E of the Europa League, with Real Sociedad claiming top spot with a superior goal difference of one.Meanwhile, Barcelona finished third in Group C of the Champions League, with Bayern Munich winning the group and Inter Milan pipping them to second place.UEFA introduced the knockout round playoffs last season.It sees a side that finished third in the Europa League group stages face a side that were relegated from third place in the Champions League group stages.The tie neutrals had hoped to see has been drawn - Manchester United will now go up against Barcelona in a blockbuster encounter.The last time the two sides met in Europe was in the Champions League campaign of 2018-19.Barcelona came out on top on that occasion with a 4-0 aggregate quarter-final victory.Cristiano Ronaldo will return to the Nou Camp, where he spent years battling Barca with Real Madrid in the El Clasico.He boasts a record of 20 goals in 34 appearances against the Blaugrana in all competitions.Meanwhile, Juventus, who finished third behind Paris Saint-Germain and Benfica in Group H of the Champions League, have drawn Ligue 1 outfit Nantes.Cristiano Ronaldo's former side Sporting CP will face Danish side Midtjylland.Shakhtar Donetsk will go head-to-head with Stade Rennais.Ajax, who came closest to winning the Europa League in 2017 when they lost to Manchester United in the final, face the impressive Union Berlin.Lastly, Bayer Leverkusen will square off against AS Monaco.However, all eyes will be on Manchester United and Cristiano Ronaldo's return to the Nou Camp to face Barcelona in a tantalizing clash.Here are some reactions from Twitter:UEFA Europa League@EuropaLeague Barcelona vs Manchester United 🏴󠁧󠁢󠁥󠁮󠁧󠁿#UELdraw340597292🇪🇸 Barcelona vs Manchester United 🏴󠁧󠁢󠁥󠁮󠁧󠁿#UELdraw https://t.co/kG6YiYq6IoThe CR7 Timeline.@TimelineCR7Manchester United and Ronaldo will face FC Barcelona in the Europa League.37529Manchester United and Ronaldo will face FC Barcelona in the Europa League.☈@TheFergusonWayFC BARCELONA vs. MANCHESTER UNITED LOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOL112354FC BARCELONA vs. MANCHESTER UNITED LOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOL.@utdcynicalJust wrap Varane and Martial up for that Barca tie and we’re fine125883Just wrap Varane and Martial up for that Barca tie and we’re fineBakosi ba nani ?@94Lundun@Cristiano life is offering you a new chance to wake up ! This is time !@Cristiano life is offering you a new chance to wake up ! This is time !Tom Young@TomYoungSJManchester United will take on FC Barcelona in the UEFA Europa League play-offs.A tremendous fall from grace from both clubs.422Manchester United will take on FC Barcelona in the UEFA Europa League play-offs.A tremendous fall from grace from both clubs.Viral Parikh@Viral1006There's no way that among 8 teams in a pot FC Barcelona gets Manchester united by chance. #UELdrawThere's no way that among 8 teams in a pot FC Barcelona gets Manchester united by chance.😂 #UELdrawPedrismo_@Pedriprop1_Man UTD vs Fc Barcelona is bigger than any UCL fixture lmao1Man UTD vs Fc Barcelona is bigger than any UCL fixture lmaoFabrizio Romano@FabrizioRomano Europa League draw: Barcelona-Manchester United. #UEL #FCB #MUFC209842855🔴 Europa League draw: Barcelona-Manchester United. #UEL #FCB #MUFCSamuel Luckhurst@samuelluckhurstFrenkie goes to Hollinwood #UELdraw35238Frenkie goes to Hollinwood 👋 #UELdraw https://t.co/hae6JfTmihPaddy Power@paddypowerBarcelona v Manchester United! #UELDraw11519Barcelona v Manchester United! #UELDraw https://t.co/mbGa1eTDI8Ashwin Kumar@ashwin_kumarVThis is actually better than the UCL matches #UELdrawThis is actually better than the UCL matches 👀 #UELdraw https://t.co/kmxqrgBhv9⬅️ #JoySportsZone ⏳️@JoySportsGHBarcelona v Manchester United What we all wanted 🏾#JoySports | #UELdraw284Barcelona v Manchester United What we all wanted 😂👏🏾#JoySports | #UELdraw https://t.co/JjndZJTs92GTV SPORTS+@mygtvsportsBarcelona fans after realizing they will be playing Manchester United in the Europa league. #GTVSports #UELdraw27Barcelona fans after realizing they will be playing Manchester United in the Europa league. 😉#GTVSports #UELdraw https://t.co/DBltT4AX08🦅@erikblancosCristiano Ronaldo will own Barcelona again in his backyard ground Camp Nou.#UELdraw1Cristiano Ronaldo will own Barcelona again in his backyard ground Camp Nou.#UELdraw https://t.co/3xdqOG5qPqFC Red Bull Salzburg EN@FCRBS_enEuropa League anthem>>>The #UELdraw is just around the corner 161Europa League anthem>>>The #UELdraw is just around the corner 🚨https://t.co/bIyGGvvo8aOwuraku Ampofo@_owurakuampofoBarcelona and Manchester United moved from playing each other in Champions League finals to meeting in the playoffs of the Europa League.#UELDraw11413Barcelona and Manchester United moved from playing each other in Champions League finals to meeting in the playoffs of the Europa League.#UELDrawDapaan@ismesharifWe getting Barca in the play off round, it was meant to be #UELdraw31We getting Barca in the play off round, it was meant to be 😂 #UELdraw https://t.co/6PeGdSQPIkUncle Wilson™@iam_wilsonsUEFA didn't disappoint with that Barcelona v Manchester United fixture. This match will get more hype than the World Cup Final. #UELdraw6510UEFA didn't disappoint with that Barcelona v Manchester United fixture. This match will get more hype than the World Cup Final. #UELdrawMike Norman@MikkyMo73The draw has just delivered the biggest tie in the history of the #EuropaLeague - Manchester United v Barcelona - and it's a play-off to get into the Round of 16 #EuropaLeague #UELThe draw has just delivered the biggest tie in the history of the #EuropaLeague - Manchester United v Barcelona - and it's a play-off to get into the Round of 16 😂 #EuropaLeague #UELCypy The Great@b1aderunner_I have taken a break from supporting Manchester united. twitter.com/EuropaLeague/s…UEFA Europa League@EuropaLeagueIt's set! 🤩Which tie are you looking forward to most?#UELdraw54811560It's set! 🤩Which tie are you looking forward to most?#UELdraw https://t.co/OvquVAv4rLI have taken a break from supporting Manchester united. twitter.com/EuropaLeague/s…Lakeside Ⓜ✨🏋@tobat02Check up on your Manchester United friends, they're going through a lot right now...Check up on your Manchester United friends, they're going through a lot right now...A Fahim Aziz@ahmedfahimazizFinally, Frenkie de Jong will entertain Manchester United fans at Old Trafford. #UEFAEuropaLeague #ManUtd #BarcelonaFinally, Frenkie de Jong will entertain Manchester United fans at Old Trafford. #UEFAEuropaLeague #ManUtd #BarcelonaBakosi ba nani ?@94Lundun@Cristiano life is offering you a new chance to wake up ! This is time !@Cristiano life is offering you a new chance to wake up ! This is time !TB@UTDalextReload this Cristiano RonaldoReload this Cristiano Ronaldo https://t.co/noWI7hW4O2Intriguing subplots emerge as Cristiano Ronaldo's Manchester United draw BarcelonaDe Jong faces the Red DevilsCristiano Ronaldo's return to Catalonia is just one of the most interesting stories to come out of Manchester United facing Barcelona in the playoffs.The Red Devils chased Barca midfielder Frenkie De Jong throughout the summer to no avail.The Dutchman was keen to play Champions League football and wanted to remain at the Nou Camp.This is despite United reportedly agreeing to an €85 million fee for the midfielder.However, De Jong now faces the side that desperately wanted him in the Europa League.He will also come up against his former manager Erik ten Hag, who coached him at Ajax to an Eredivisie title.Gerard Pique has retired just before potentially facing his former side.The legendary defender left Old Trafford in 2008 and returned to Barca for €5 million.He then won the Champions League the season after with a 2-0 win over United in the final.