Chelsea currently find themselves at the most testing point of the season.Having started out decently, the club now find themselves effectively out of the title race. The UEFA Champions League triumph from last season was followed up by a strong transfer window. It had fans believing the club was ready to challenge for the Premier League.The marquee re-signing of Romelu Lukaku and the loan deal for Saul Niguez was a strong statement from the side. They were looking to challenge for their first Premier League title in over five years.ESPN FC@ESPNFC"As they're off celebrating like they've won the World Cup, Manchester City are racking up a 16 point lead on Chelsea where it really matters: the Premier League. ... I don't buy £100M strikers to win the bloody Club World Cup."- @CraigBurley 🗣6:10 AM · Feb 13, 202257841023"As they're off celebrating like they've won the World Cup, Manchester City are racking up a 16 point lead on Chelsea where it really matters: the Premier League. ... I don't buy £100M strikers to win the bloody Club World Cup."- @CraigBurley 🗣 https://t.co/jJd3SllnD0Half a season later, the Blues have simply underperformed. The squad has failed to live up to the expectations of fans and now find themselves in third place in the Premier League table. They are 16 points behind leaders Manchester City with only 14 games to go this season.The reason for this is quite obvious. There have been a few players that have underperformed for the Blues this season and below, we take a look at five of them.#5. Saul NiguezSaul Niguez's signing has turned out pretty bad so farSaul Niguez signed a loan deal from Atletico Madrid in the summer transfer window.The Spaniard has shown his class over the years for the Madrid outfit and was expected to add some depth to the Blues' midfield this season. His move so far has yet to justify itself.B/R Football@brfootballOFFICIAL: Chelsea confirm the signing of Saul Niguez on a season-long loan from Atletico Madrid 4:18 AM · Sep 1, 2021193741344OFFICIAL: Chelsea confirm the signing of Saul Niguez on a season-long loan from Atletico Madrid 🔵 https://t.co/mCrIAQuSfLSaul is undoubtedly an excellent midfielder and boasts world-class attributes. However, his career in London got off to a disastrous start when he made his debut against Aston Villa, where he looked completely off the pace. He had to be substituted at half-time by manager Thomas Tuchel.WhoScored.com@WhoScored⏱️ Most minutes played of Chelsea midfielders this seasonJorginho - 1071Mateo Kovacic - 1006Mason Mount - 763N'Golo Kante - 519Ruben Loftus-Cheek - 496Ross Barkley - 270Saul Niguez - 270 Better call... his agent?4:03 AM · Nov 9, 20212219146⏱️ Most minutes played of Chelsea midfielders this seasonJorginho - 1071Mateo Kovacic - 1006Mason Mount - 763N'Golo Kante - 519Ruben Loftus-Cheek - 496Ross Barkley - 270Saul Niguez - 270☎️ Better call... his agent? https://t.co/kREAFiqESRSince then, Saul has certainly improved but is still a shadow of the player we have seen at Atletico over the years. With more than half the season complete, the 27-year-old has yet to provide any substantial contributions to the side.#4. Christian PulisicChristian Pulisic has failed to build on his last season's performanceChristian Pulisic has been extremely inconsistent over the course of the season.The attacker was signed from Borussia Dortmund in 2019 for a reported £58 million, becoming the most expensive American player of all time. His time since has been marred by injuries and inconsistent form.SPORTbible@sportbibleBREAKING: Chelsea have signed Christian Pulisic from Borussia Dortmund for £58M, loaning him back to Borussia Dortmund for the rest of the season.2:48 AM · Jan 2, 201969599BREAKING: Chelsea have signed Christian Pulisic from Borussia Dortmund for £58M, loaning him back to Borussia Dortmund for the rest of the season. https://t.co/d9Oe5hQmSqIt goes without saying that Pulisic can be lethal on his day. Blessed with electric pace and impressive finishing ability, Pulisic is certainly a bonafide attacking threat on the wings.But since joining the Londoners, Pulisic has missed several games through injury. He has made 20 appearances this season across all competitions, registering a mere three goals.Pulisic will need to pull up his socks if the Blues are to challenge for the UEFA Champions League once again this season.