The Roman Abramovich era has been defined by superstar signings and success in the senior team. Behind closed doors, however, significant financial investment has been made to make Chelsea one of the finest football academies in Europe. With seven FA Youth Cups, four UEFA Youth Leagues and two U-18 National Championships victories in the last decade, the young blues have excelled over the years.Whilst the senior team roster over the last two years boasts stars such as Reece James, Mason Mount, Fikayo Tomori, Ruben Loftus-Cheek and Callum Hudson-Odoi, the successful jump from the youth team has looked impossible at times. Several talented youngsters who preceded them have been forced out on loan and left the club without breaking into the first team.On that note, here are five infamous members of Chelsea's loan army over the years.#5 Jeffery BrumaChelsea v Aston Villa - FA Youth Cup Final 2nd LegDutch center-back Bruma had been with Chelsea since the age of 15 and was part of Chelsea's inaugural "golden boy" batch of 2010. Skilled on the ball and blessed with natural physical ability, Bruma looked to be an alternative center-back option to the likes of John Terry and Alex.In the 2010-11 season, he was loaned out to Leicester City in need of senior-level playing time, a move which saw him never make another appearance for the club again. He has represented the likes of PSV Eindhoven, Wolfsburg, Schalke and Mainz, among others, but has failed to live up to his potential. 19y 150d - @OfficialASRoma's Justin Kluivert will become the second youngest Dutch player to start a Champions League game for a foreign team, after Jeffrey Bruma (19y 10d in 2010, for Chelsea). Promise. pic.twitter.com/nAxmLMYqvz— OptaJohan (@OptaJohan) October 2, 2018Bruma has been capped 25 times by the Netherlands, making him far more successful than most other players on this list. Nevertheless, he remains one who could not live up to his immense potential.#4 Nathaniel ChalobahChelsea v Peterborough United - The Emirates FA Cup Third RoundNathaniel Chalobah was a widely lauded player who spent over 12 years under Chelsea's umbrella. Making 97 appearances for England across different age groups - one of which was for the senior team - Chalobah was, in many ways, a lost talent disheartened by Chelsea's loan system.The talented holding midfielder made his way up the ranks as a dependable footballer capable of playing in three different positions. As first-team opportunities came few and far, Chalobah grew into senior-level football through a number of loan spells at Watford, Nottingham Forest, Middlesbrough, Burnley, Reading and Napoli.Chelsea have 25 players on loan at clubs around England and Europe.Nathaniel Chalobah didn't want to be the 26th.https://t.co/5xsQDfoKzQ pic.twitter.com/aCywmSjLyJ— BBC Sport (@BBCSport) August 5, 2017Seemingly never a part of the first team plan under Antonio Conte, he decided to seek a new permanent home and moved to Watford in a deal worth £5 million. At Watford, he has been a regular in the starting XI over the past three seasons, as the Hornets look to re-establish themselves in the Premier League after securing promotion.