Midfielder: Mesut Ozil (Arsenal)

Ozil's performances for Arsenal were one of the worst in Europe during last season. Indeed, the German international was often at the centre of criticism. His performances were questioned not only by fans but also by a couple of Arsenal's former players, like Emmanuel Petit and Martin Keown.
Ozil was widely accused of being lazy and disinterested with some claiming that the criticism is built on solid facts and others that Ozil's takes the role of a scapegoat in Arsenal's general crisis.
Midfielder: Tiemoue Bakayoko (Chelsea)

In July 2017, Chelsea spent €40 million to get Bakayoko from Monaco after an impressive season of his for the Monegasques. However, the defensive midfielder kept on underperforming for the Blues during last season.
According to the statistics, Bakayoko's performances were indeed among the worst in the Chelsea squad during the 2017-18 season. He led his team in critical defensive errors. Moreover, he averaged a career-low of 1.3 interceptions per game and a career second-worst 1.2 successful ball clearances.
The aforementioned facts argue that Bakayoko could not justify the sum that Chelsea paid to Monaco a year ago. He currently plays at AC Milan on a loan.
Midfielder: Wesley Sneijder (Nice)

The Dutch maestro joined Nice on August 2017 on a free transfer but failed to make an impact. Sneijder featured only 8 times for the French club with zero goals and only one assist before departing in order to join Al Gharafa in January.
Midfielder: Ganso (Sevilla)

Ganso joined Sevilla from Sao Paulo in 2016 for €10 million but failed to prove himself at the Ramón Sánchez Pizjuán Stadium. During the 2017-18 campaign, the attacking midfielder made only 11 appearances for Sevilla, scoring 4 goals and setting up another 3.
Ganso was considered a very promising player during his Sao Paulo spell where, along with Neymar, he put on display some exceptional performances that made some people regard him as one of the best in his position in the world. However, he clearly failed to shine in the higher level football of Europe.
The 28-years-old currently plays at SC Amiens on loan from Sevilla.