Barcelona fans are raging with Xavi Hernandez's decision to start Marcos Alonso at left-back for their huge clash with Bayern Munich at the Allianz Arena in the Champions League.Gameweek 2 of Europe's elite club competition throws up the most tantalizing fixture of the group stages on September 13.Barcelona are looking to build on their 5-1 thrashing of Viktoria Plzen against a Bayern side who are in fine form.However, Blaugrana fans are less than impressed with Xavi's choice of left-back with new signing Alonso coming into the XI.The Spaniard joined Barca from Chelsea on a free transfer and is set to make his first start in the Champions League with the Catalan giants.Meanwhile, Marc-Andre ter Stegen starts in goal with Ronald Araujo, Andreas Christensen and Jules Kounde joining Alonso in defense.Sergio Busquets, Pedri and Gavi are selected in midfield, whilst Ousmane Dembele and Raphinha will provide width on the wings.The man of the moment, starts against his old side in what promises to be an enthralling night for the legendary Pole.All eyes will be on whether Bayern defenders can stop their former teammate who started the Champions League campaign off with a hat-trick against Plzen.FC Barcelona@FCBarcelonaBarça XI#BayernBarça154482142Barça XI#BayernBarça https://t.co/1Annds5tNzHowever, Barca fans are slamming Xavi's decision to start Alonso and here are some reactions from supporters on Twitter:🇳🇱 Factos 👍👀@DaDavey__@FCBarcelona @ChampionsLeague Inshallah Alonso ball2303@FCBarcelona @ChampionsLeague Inshallah Alonso ball https://t.co/bJ4efnwL6fViserys 🪝@ThePrimeCuler@FCBarcelona @ChampionsLeague Xavi let’s see what you’re cooking with Alonso because bruh29@FCBarcelona @ChampionsLeague Xavi let’s see what you’re cooking with Alonso because bruh𝑀🥷🏽@fcbmox@FCBarcelona @ChampionsLeague Alonso1001@FCBarcelona @ChampionsLeague Alonso https://t.co/GUkYmQna4qLaportabuymæhle@Vamosbarca101@FCBarcelona @ChampionsLeague Alonso over balde wtf29@FCBarcelona @ChampionsLeague Alonso over balde wtfFlame🌍@phatdem@FCBarcelona @ChampionsLeague alonso sigh@FCBarcelona @ChampionsLeague alonso sighJosen¹⁴ 🇧🇩@BarcaEra1@FCBarcelona @ChampionsLeague Alonso really? That guy last played in 29 april xavi2112@FCBarcelona @ChampionsLeague Alonso really? That guy last played in 29 april xavi𝐂𝐎𝟐𓅓@C_SYM1@FCBarcelona @ChampionsLeague Alonso uno, jesus.. he said his picking form over experience and he starts Alonso what a fraud2@FCBarcelona @ChampionsLeague Alonso uno, jesus.. he said his picking form over experience and he starts Alonso what a fraudBlaugrana💙❤️@Blaugrana44life@FCBarcelona @ChampionsLeague Alonso? Yeah it's a wrap boys@FCBarcelona @ChampionsLeague Alonso? Yeah it's a wrap boysEDWARD👽@_pandax1@FCBarcelona @ChampionsLeague Xavi what is this ?? Alonso?11@FCBarcelona @ChampionsLeague Xavi what is this ?? Alonso?Rena🥺😍@_AyenihannahI would humbly like to change my prediction to 4-1 Bayern win now that I have seen that Alonso starts officially.Also, he will get a yellow in the first 20 minutes and a red if not substituted. twitter.com/FCBarcelona/st…FC Barcelona@FCBarcelonaBarça XI#BayernBarça12280Barça XI#BayernBarça https://t.co/1Annds5tNzI would humbly like to change my prediction to 4-1 Bayern win now that I have seen that Alonso starts officially.Also, he will get a yellow in the first 20 minutes and a red if not substituted. twitter.com/FCBarcelona/st…Barcelona eye revenge against Bayern Munich Barca were torn apart by the Bavarians last seasonBarcelona made an early exit from last season's Champions League and that was mostly down to their two defeats to Bayern in the group stages.It was the first time in 20 years that Barca had exited Europe's elite club competition at the group stage.The La Liga giants were beaten 3-0 by the Bavarians both home and away in what was a difficult period for the Nou Camp side.However, Xavi Hernandez oversaw a huge transformation of the Catalan giants that saw him take them from ninth in the league to a second-placed finish.The signing of former Bayern hitman Robert Lewandowski has only added to what was already an exciting squad at Xavi's disposalThe Pole has flourished at the start of the season with nine goals in six appearances.Football on BT Sport@btsportfootballHe scored 344 times in 374 games for Bayern Munich Tonight, Robert Lewandowski lines up against his former side for Barcelona. Here are five of the Poland striker's best Champions League goals for the German outfit.#UCL82847He scored 344 times in 374 games for Bayern Munich ✨Tonight, Robert Lewandowski lines up against his former side for Barcelona.🎥 Here are five of the Poland striker's best Champions League goals for the German outfit.#UCL https://t.co/PXFQZOvi1YThe legendary forward hit a mesmerizing hat-trick against Plzen in Barcelona's Champions League opener last week.It bodes well for the Blaugrana as they look to challenge amongst Europe's elite once again this season.They come up against a Bayern side who will be a real test of just how far Xavi's side have come.