Like every club in Europe, Arsenal have had their fair share of hits and misses when it comes to player transfers.A lot of top players have taken the stage at the Emirates and performed at a high level, with some of them even having the spells of their careers at Arsenal. The opposite has been the case for some others, though, as they struggled during their time at the North London club.While some of these 'flops' had themselves to blame, some others failed to shine because of some questionable and wrong transfer decisions by Arsenal.On that note, let's take a look at the five biggest transfer mistakes by Arsenal.#5 Arsenal's sale of Cesc Fabregas to Barcelona (€29m)Cesc Fabregas (left)Cesc Fabregas began his career at Barcelona's La Masia academy, but due to a shortage of playing time, he made the switch to join Arsene Wenger at Arsenal in 2003.The Spaniard, who spent eight seasons at Arsenal, became the youngest ever player to play for the club's senior team. He was also the youngest goal-scorer in the club's history and was named the club captain at the age of 18.Arsenal midfield trio of Jack Wilshere, Cesc Fabregas and Aaron Ramsey during a training session 10 years ago. [Scott Heavey, 2011] pic.twitter.com/qr1aoWCsoT— Throwback Arsenal (@ThrowbackAFC) March 9, 2021However, a protracted transfer saga between Arsenal and Barcelona, which stretched across three transfer windows, saw the Spaniard move to the Camp Nou in 2011.In all fairness to Arsenal, Cesc Fabregas was bent on moving to Barcelona, and the Spanish club harped on that desire to a rather disrespectful point.However, Arsenal should have tried harder to retain the services of their star midfielder, as Fabregas' departure heralded a downward spiral at the Emirates to a certain degree.#4 Signing of Nicolas Pepe from Lille (€80m)Nicolas Pepe (left)Arsenal signed Nicolas Pepe from Lille in the summer of 2019 after the Ivorian scored 22 goals and assisted 11 in the Ligue 1.It was a smart move from the London club to acquire a player with such productivity. However, Arsenal paid a staggering €80m for Pepe after the player has just one outstanding season at Lille.While the deal looked fair enough initially, it has now proved grossly imprudent in hindsight, as the winger has come nowhere close to his Lille numbers.50 - Nicolas Pepe has become the first player to successfully dribble past Virgil van Dijk in the Dutch defender's last 50 appearances in the Premier League, since Mikel Merino in March 2018 for Newcastle. Beaten. pic.twitter.com/B1oRZMciOB— OptaJoe (@OptaJoe) August 24, 2019Prior to his breakout season at Lille, Pepe scored fewer goals in his previous two seasons combined, so Arsenal's decision to break their transfer record for the winger was not the wisest thing to do.Pepe managed just eight goals in his debut season at Arsenal and has scored another eight so far this season.