German tactician Jurgen Klopp is regarded as one of the best managers in football, especially since he took charge of Liverpool back in 2015.Although the Reds' ownership (Fenway Sports Group) does not have the financial power to match Manchester City's spending, Liverpool have kept pace with Pep Guardiola's side.The bulk of the credit goes to Klopp, who has led the club to five trophies since arriving on Merseyside, including the 2020 Premier League title and the 2019 UEFA Champions League.Squawka@SquawkaJurgen Klopp has now won each of his last four major cup finals for Liverpool: 2018/19 Champions League 2019/20 UEFA Super Cup 2019/20 Club World Cup 2021/22 League CupHe has the winning formula. ‍2:00 AM · Feb 28, 2022821155Jurgen Klopp has now won each of his last four major cup finals for Liverpool:🏆 2018/19 Champions League🏆 2019/20 UEFA Super Cup🏆 2019/20 Club World Cup🏆 2021/22 League CupHe has the winning formula. 👨‍🔬 https://t.co/NGRX2M0hduLiverpool have made shrewd signings under Jurgen KloppThe German manager's record during his reign at Anfield is exemplary. Liverpool have won 226 of Klopp's 363 games as head coach so far, losing just 62 times.The free-scoring Reds have found the back of the net over 750 times while conceding under 400 goals.From Mohamed Salah and Sadio Mane to Virgil van Dijk and Andrew Robertson, Liverpool's transfer business under Klopp has been sensational. However, there has been the occasional blip that hasn't worked out as planned.On that note, we look at five players who failed to deliver under the German coach:#5 Naby KeitaNaby Keita's time at Anfield has been ruined by injuries.The Reds shelled out £54 million for RB Leipzig's Guinean midfielder Naby Keita in 2018, making him the third-most expensive signing of Klopp's managerial career.Unfortunately, the 27-year-old star's spell at Anfield has been hampered by constant injury issues. Keita has suffered nearly 15 different issues since arriving at the club, causing him to miss over 50 games.Squawka@SquawkaNaby Keïta's best scoring seasons in the Premier League:◎ 2018/19: 25 games, 2 goals◎ 2019/20: 18 games, 2 goals◉ 2021/22: 6 games, 2 goalsHe's found his shooting boots.9:13 AM · Oct 24, 2021724102Naby Keïta's best scoring seasons in the Premier League:◎ 2018/19: 25 games, 2 goals◎ 2019/20: 18 games, 2 goals◉ 2021/22: 6 games, 2 goalsHe's found his shooting boots. https://t.co/Oe6mMrf2QOIn his four seasons at the club so far, Keita has managed to hit 20 league appearances just once. He has featured in 101 games for Klopp, scoring ten times and assisting five goals.Considering Liverpool and Klopp's impressive record, Keita's signing remains a rare miss.#4 Dominic SolankeDominic Solanke's development stalled under Jurgen Klopp.Back in 2017, Dominic Solanke was arguably the hottest prospect in English football.The Chelsea youth product played a starring role as England won the 2017 U-17 European Championship and the 2020 FIFA U-20 World Cup. Solanke scored four goals in each of the two tournaments.SPORTbible@sportbibleLiverpool - The kings of selling players! Solanke - £19m Sakho - £26m Benteke - £27m Ings - £20m Ibe - £15m Joe Allen - £14mthesportbible.com/football/news-…4:00 AM · Jan 5, 201963997Liverpool - The kings of selling players! 🙌✅ Solanke - £19m✅ Sakho - £26m ✅ Benteke - £27m✅ Ings - £20m ✅ Ibe - £15m ✅ Joe Allen - £14mthesportbible.com/football/news-…Liverpool convinced the centre-forward to switch allegiances from his boyhood club and join the Merseyside outfit in 2018. However, Solanke's development stalled under Jurgen Klopp and the striker struggled for form and opportunities.He was sold to Bournemouth in 2019 for £19 million after scoring just once in 27 appearances for Liverpool.#3 Marko GrujicMarko Grujic (R) in action against Tottenham HotspurSerbian defensive midfielder Marko Grujic arrived at Liverpool as a highly rated 20-year-old back in 2016 for a fee of £6 million. Seven years later, he has made just 16 appearances for the Reds, scoring and assisting once apiece.Despite leaving on loan thrice, Grujic is somehow still a Liverpool player, although he is expected to join Porto on a permanent move at the end of the ongoing season.Although Klopp has played a key role in the development of numerous players in his managerial career, Grujic was a budding star who failed to kick on under the German coach.#2 Alexander Oxlade-ChamberlainJurgen Klopp and Alex Oxlade-Chamberlain celebrate a winThe Reds paid Arsenal nearly £35 million for Alex Oxlade-Chamberlain back in 2017.The Englishman was considered a unique talent at the time as he had the pace and dribbling to play on the flanks but also the technique to play in the middle of the park.Liverpool FC@LFCAlex Oxlade-Chamberlain is a Red. lfc.tv/Oxlade-Chamber…4:32 AM · Aug 31, 2017137576467Alex Oxlade-Chamberlain is a Red. 🔴 lfc.tv/Oxlade-Chamber… https://t.co/dQQvHcMixBDespite flashes of potential, though, Chamberlain's time at Anfield has been a mixed bag. Injuries have played their part but now, with the midfielder on the verge of turning 30, it feels as though he never realized his full potential.Chamberlain's versatility has proved to be a double-edged sword, as Klopp has deployed him in a plethora of positions.Now in his fifth year at the club, the midfielder has hit 20 league appearances in only two seasons, and has scored just 17 times in 133 games, to go with 14 assists.#1 Loris KariusLoris Karius endured a torrid time at AnfieldJurgen Klopp raided his former club Mainz 05 to sign young German keeper Loris Karius for £5.5 million in 2016. Touted as a potential successor to Manuel Neuer at the international level, Karius arrived at Anfield with a glowing reputation.It quickly turned into a nightmare, the lowlight of which was a disastrous showing in the 2018 Champions League final against Real Madrid.Karius turned in one of the worst performances in the history of the competition, gifting Real Madrid two goals as they romped to a 3-1 win.ESPN FC@ESPNFCLoris Karius apologises to Liverpool fans following last night's Champions League nightmare. es.pn/2ISwNSU9:16 AM · May 27, 2018923282Loris Karius apologises to Liverpool fans following last night's Champions League nightmare. es.pn/2ISwNSU https://t.co/c7B7tm5MpEThe keeper's career spiraled after that fateful night and loan spells to Besiktas and Union Berlin failed to help him rediscover his confidence. Karius is still at Liverpool and could finally leave at the end of the ongoing season.The 28-year-old has made 49 appearances for the Reds, conceding 47 goals and registering 22 clean sheets.