Paris Saint-Germain find themselves just past the midway point in what has been described as a defining season for the club.Boasting star power like no other club, PSG have had high expectations of them over the past few years. The club have dominated Ligue 1 over the years, but is yet to taste success in the UEFA Champions League.Eurosport@eurosport🤔 Can PSG win the Champions League this season?3:00 AM · Feb 15, 202261🔵🤔 Can PSG win the Champions League this season?The statement signings of Neymar, Kylian Mbappe, and most recently Lionel Messi, have only made expectations soar. With the appointment of Mauricio Pochettino as head coach, the side seemingly have no excuse when it comes to challenging for Europe's top prize.Let's take a look at five PSG players who have underperformed this season.#5. Thilo KehrerParis Saint Germain v RC Strasbourg - Ligue 1 Uber EatsThilo Kehrer has found himself under the microscope with his performances of late.The German was signed in 2018 for a reported €37 million from Schalke. Kehrer is an extremely versatile player and is capable of playing anywhere along the backline. He has, on occasion, been used in midfield as well to great effect.Paris Saint-Germain@PSG_English🥵 @nunomendes_35🤩 Thilo Kehrer #PasseDé, presented by autohero.com/fr#PSGSB29 5:48 AM · Jan 17, 202228115🥵 @nunomendes_35🤩 Thilo Kehrer📺 #PasseDé, presented by autohero.com/fr#PSGSB29 https://t.co/fNm4dcopa5Kehrer has now made over 100 appearances for the club and is widely seen as an impactful player when deployed in the right position. His performances this season have not been up to the mark and have resulted in the 25-year-old becoming the target of criticism.Kehrer has been used as a center-back and a right-back this season, but has failed to offer the quality that is expected of him from Mauricio Pochettino.#4. Abdou DialloClub Brugge KV v Paris Saint-Germain: Group A - UEFA Champions LeagueAbdou Diallo is another player who has yet to come into his own during his time at PSG.Diallo joined PSG in 2019 after a year with Borussia Dortmund. He was excellent for the German heavyweights and earned the attention of Europe's elite with his performances.Since joining PSG, Diallo's impact has been underwhelming. A center-back by trade, he has failed to live up to the lofty standards set by Marquinhos and Presnel Kimpembe in the same position.#3Sports@3SportsGhPSG gave a heroes welcome to #AFCON2021 winners Abdou Diallo and Idrissa Gueye before their game against Rennes. #3Sports2:31 AM · Feb 12, 202290254PSG gave a heroes welcome to #AFCON2021 winners Abdou Diallo and Idrissa Gueye before their game against Rennes. #3Sports https://t.co/phGgKIrsr7Diallo recently won the Africa Cup of Nations trophy with Senegal, contributing immensely to the success. Still only 25, Diallo has a long road ahead of him.