Roman Abramovich's era at Chelsea has seen some of the finest midfielders in club football history wear the Chelsea blue. Notable examples include all-time top scorer Frank Lampard, the magnificent Michael Ballack, the excellent Michael Essien and modern superstars N'Golo Kante and Jorginho. These names prove that Chelsea have always had marquee talents in midfield.Some ambitious signings in midfield, however, were complete disasters. These players failed due to a number of reasons. A few where an uncomfortable fit in a tactical system while others lacked the technical ability to match the pace of the Premier League. Some players were just overexpensive purchases made by the club amidst the hype.Keeping those factors in mind, here are five of the worst midfield signings Chelsea have made under Roman Abramovich's reign:#5 Juan Sebastian VeronChelsea show off new signings Joe Cole and Juan Sebastian Veron.Juan Sebastian Veron was amongst the top talents in Serie A in the late 90s. He played a starring role for the likes of Parma and Lazio as a creative attacking midfielder.Veron's performances were so distinguished that he found himself on the prestigious "FIFA 100" list for the 20th century. He was selected alongside the likes of the late Diego Maradona. It was this player that Manchester United splurged a £28 million transfer fee on, only to see Veron falter and stutter at Old Trafford.He was soon deemed excess to United's needs and Chelsea came in with a £14 million fee, nearly half of what Manchester United paid. Unfortunately a change in environment was hardly conducive to success. Veron featured in just seven league appearances, though he did score a winner against Liverpool in that time.Chad ⭐⭐@ChelseaChadderOn this day: 2003 - Juan Sebastian Veron scored his only @ChelseaFC goal. #CFC #Chelsea5:30 AM · Aug 17, 20176421On this day: 2003 - Juan Sebastian Veron scored his only @ChelseaFC goal. #CFC #Chelsea https://t.co/k06YmcQp1wMultiple injuries and a lack of form and confidence meant Veron was reduced to a shadow of his former self, as the gamble to bring him to Chelsea failed. The Argentine was promptly packed off on loan to Inter Milan. He spent two more successful seasons in a familiar environment, before going back home to Argentina with Estudiantes.#4 Shaun Wright-PhillipsFormer Chelsea midfielder Shaun Wright-Phillips.Recognized as a prodigious talent, Manchester City snapped up Shaun Wright-Phillips as a teenager where he enthralled fans with his speed and wing play.Wright-Phillips was an established England international by the time Chelsea came calling with a £21 million offer in 2005, when he was aged just 23. The Englishman was a fan favorite under Jose Mourinho, but never got a prolonged run in the first-choice winger slot.A three-year career with over 125 appearances, as well as Premier League and FA Cup winners' medals, is hard to designate as a failure. But there lingers a constant feeling that Wright-Phillips never reached his potential and was a goal shy attacker.Chad ⭐⭐@ChelseaChadderOn this day: 2007 - Shaun Wright-Phillips scored THIS goal for #Chelsea (vs Tottenham). #CFC2:30 AM · Mar 19, 2020477On this day: 2007 - Shaun Wright-Phillips scored THIS goal for #Chelsea (vs Tottenham). #CFC https://t.co/Z7WaIOS7dZPlaying under Jose Mourinho, Avram Grant and Luiz Felipe Scolari, Wright-Phillips was always competing to prove his worth at club level. This ultimately compromised his England international status.In 2008, Wright-Phillips moved back to Manchester City for just a third of his initial transfer fee. He spent three more seasons under the new Abu Dhabi-based ownership before playing for Queens Park Rangers. Wright-Phillips then called time on his career after a spell in the United States with the New York Red Bulls.