Premier League champions Liverpool won their first pre-season friendly 3-0 against German side VfB Stuttgart on a rainy evening in Austria.Roberto Firmino, Naby Keita and Rhian Brewster scored for Jurgen Klopp's champions as the newly-promoted Bundesliga side looked no match for Liverpool, who looked as sharp as the circumstances allowed them to be.Firmino put the Reds in front, after brilliant work from Curtis Jones on the left flank. The young Scouser dribbled his way to the byline, and then managed to cut it back for Firmino to tap into an empty net.Well in, Reds 💪🔴A good start to our pre-season campaign 👊— Liverpool FC (@LFC) August 22, 2020The Brazilian turned from scorer to provider at the end of the half, when he set up Keita with a lovely back-heel, that left him one-on-one with the Stuttgart goalkeeper. The Guinean made no mistake with the finish and put the Reds two goals to the good.Klopp made 11 changes at half-time, with new signing Kostas Tsimikas making his first appearance in a Liverpool shirt. The Reds' lead was extended midway through the half, with an excellent team goal.After a superb passing sequence between Harvey Elliott, Marko Grujic and James Milner on the right flank, the veteran set up Brewster for an easy finish to round off the evening for the Reds.Here are five things that we learned from the game, as Klopp's men step up their preparations for the new season with another friendly against RB Salzburg on Tuesday.#5 The conditions hampered the flow of the gameMohamed Salah's movement was severely hampered by the conditions (Image Courtesy: Liverpool FC)The rain absolutely bucketed down in Saalfelden as the Reds got their pre-season friendlies again. Jurgen Klopp started with a strong enough enough team, with only Neco Williams and Curtis Jones starting in what was otherwise a team you would expect to start in the Premier League.Liverpool managed to keep possession well enough, but their ability to exchange quick passes and use the pace of Mohamed Salah and Sadio Mane were severely hampered by the heavy rain. The pitch had become soaked, and the ball wasn't really rolling smoothly on it.The weather relented a lot more in the second half, but the pitch had already taken enough of a battering. That meant the likes of Nat Phillips and Sepp van den Berg, the young Liverpool centre-back pairing in the second half, were very nervous about their distribution from the back, especially with not being able to judge the weight of passes correctly.Klopp obviously knows better than to judge from just this one game, but he will be relieved that he didn't have more injuries to deal with, after Divock Origi, Xherdan Shaqiri and Alex Oxlade-Chamberlain all missed out this evening."The weather! Wow!" was Klopp's first reaction to proceedings, when he was interviewed by LFC TV after the match.#4 Naby Keita set for big Liverpool seasonNaby Keita scored Liverpool's second goal of the game (Image Courtesy: Liverpool FC)Naby Keita joined Liverpool for RB Leipzig two summers ago amid much expectation and fanfare. But right now, his Liverpool career is very much at a crossroads. When he has played, he has always been an influential player for Klopp's side. However, he just has not been available for long enough, or consistently enough.He was one of Liverpool's best players in the last nine Premier League games after the league's restart post-lockdown, and in this game, he seemed to take that form forward. He was the one Liverpool player in the first half who looked unperturbed by the conditions.NABY LAD 😄#LFCPreSeason pic.twitter.com/eG4wSYQ2cs— Liverpool FC (@LFC) August 22, 2020His dribbling was still top-notch, and he was linking up brilliantly with the Reds' forward players. Sadio Mane should've scored after a lovely one-two with Keita put the Senegalese through on goal, but his touch deserted him.The goal was just reward for Keita on the night, for another sharp and purposeful performance. Klopp will only hope that he can remain fit to provide more such influential performances through the course of the Reds' title defence in the upcoming season.