Liverpool head coach Jurgen Klopp will take on his former side Mainz in a pre-season friendly scheduled to take place on Friday.Liverpool played out draws with German sides Stuttgart and Wacker Innsbruck in their two mini-matches played on Tuesday. The Reds had an underwhelming 2020-21 Premier League campaign by their standards and Klopp will be looking to get back in contention for the championship once again in the forthcoming season.Liverpool's first league game will be against promoted side Norwich City on 14 August, and they are set to play Hertha Berlin, Athletic Club and Osasuna before that.Meanwhile, Mainz kicked off their pre-season with a 2-1 victory over Wurzburger Kickers. They will begin their league campaign with a game against RB Leipzig on 15 August.Mainz vs Liverpool Head-to-HeadLiverpool and Mainz have been pitted against each other twice so far. The Bundesliga team prevailed in both meetings.The last meeting between the two teams ended in a 4-0 win for Mainz.Mainz form guide: D-W-W-D-WLiverpool form guide: W-L-D-D-DAlso See: Fabrizio Romano's Transfer Roundup: Update on Manchester United's transfer plans, Barca's plan for Antoine Griezmann, and moreMainz vs Liverpool Team NewsMainzMainz manager Bo Svensson has a 29-man squad to choose from, and he will likely field two different sides for either half of the game. Under-19 stars Timothe Rupil and Ben Bobzien are expected to play significant parts in the match.Mainz have no injury concerns going into Friday's encounter.Injured: NoneDoubtful: NoneSuspended: NoneAnother day of hard work begins 💪#Mainz05 pic.twitter.com/ILrG1Ymp1H— Mainz 05 English (@Mainz05en) July 21, 2021LiverpoolThe game comes too soon for centre-backs Virgil Van Dijk and Joe Gomez, both of whom are still recovering from knee injuries. They are making steady progress, and Reds fans will be hoping they return to action before the start of the league campaign.Players involved in Copa America and Euro 2020 have been given a few days off, which could lead to Klopp tinkering with his formation and starting lineup.Injured: Virgil Van Dijk and Joe GomezDoubtful: NoneSuspended: NoneMainz vs Liverpool Predicted XIMainz predicted XI (3-1-4-2): Finn Dahmen; Jeremiah St. Juste, Stefan Bell, Moussa Niakhate; Dominik Kohr; Kevin Stoger, Leandro Barreiro, Jean-Paul Boetius, Daniel Brosinski; Karim Onisiwo, Adam SzalaiWorking towards our peak ⛰️ pic.twitter.com/C6wXebluh5— Liverpool FC (@LFC) July 21, 2021Liverpool predicted XI (4-3-3): Adrian; Trent Alexander-Arnold, Joel Matip, Rhys Williams, Konstantinos Tsimikas; James Milner, Naby Keita, Harvey Elliott; Sadio Mane, Divock Origi, Takumi MinaminoMainz vs Liverpool PredictionLiverpool are expected to feature a much weaker side than Mainz on Friday, which makes the latter the favorite to win this game.We predict that Mainz will win this clash comfortably.Prediction: Mainz 3-1 Liverpool