Serge Gnabry (Werder, Aug 2016, £5m)
The German's progress at Arsenal was hampered by a knee injury. A lack of first-team chances forced the forward to seek career opportunities elsewhere and he decided to move to his motherland.
11 goals in 27 Bundesliga games at Werder grabbed Bayern's attention who couldn't miss the chance to sign the rising talent for £7m as they activated a clause in his contract.
Gnabry was sent on loan for the 2017/18 campaign to Hoffenheim to enjoy another successful season - 10 goals plus 7 assists in 26 Bundesliga appearances as his side finished third in the league and won a Champions League spot.
Since 2018, the winger has been enjoying constant progress. The 25-year-old is a first-team regular both for Bayern and Germany. He's won 2 Bundesliga titles, 2 German Cups and a Champions League trophy. Serge seems to have left his injury woes behind and his best years are still probably ahead of him.
Wojciech Szczesny (Juventus, July 2017, £10m)
Initially loaned out to Roma in 2015, the Pole spent 2 seasons with the Giallorossi as a first-choice keeper before joining Juventus permanently on a four-year contract.
Szczesny was Gianluigi Buffon's understudy in his maiden season as he kept 11 clean sheets in the 17 Serie A games.
Wojciech inherited the number 1 shirt as the Italian legend moved to PSG ahead of the 2018/19 campaign. He remains Juve's main goalie to this day winning four major trophies.
The 30-year-old signed a contract extension until 2024 last season. It seems like the Pole will be the first-choice keeper with the Old Lady for many more years if he keeps his form and avoids injuries.
Alexis Sanchez (Manchester United, Jan 2018, direct exchange for Mkhitaryan)
The Chilean signed a super-lucrative contract (around £400,000-a-week basic salary) with the Red Devils but he never produced a return similar to what he had at Arsenal. 5 goals and 9 assists across 45 games in 1.5 years with United.
In August 2019, he joined Inter on loan before signing a permanent contract with the Nerazzurri on a three-year deal as a free agent the following summer.
The forward has managed 6 goals and 13 assists in 47 games with the Serie A outfit.
Now, aged 32 he looks a shadow of himself comparing with his Arsenal or Barcelona days. Occasional moments of brilliance can't hide his long-term decline. Inter will probably be the last big club in his career.
Aaron Ramsey (Juventus, June 2019, free agent)
After 11 seasons with the Gunners, the Welshman opted to join the Old Lady as Arsenal could match their contract offer.
In his first season, Rambo scored just 4 goals and bagged an assist as he was chiefly used as a sub by Maurizio Sarri.
Under Andrea Pirlo this season, the 30-year-old has made 8 starts in 10 Serie A games along with 4 starts in 5 Champions League matches delivering 3 assists.
The midfielder's contract with Juve will expire in 2023.
Henrikh Mkhitaryan (Roma, June 2020, released for free)
Micki's main problem at Arsenal was lack of consistency. He had some really good performances but overall his 1.5 years with the Gunners were quite average.
In September 2019, he moved to Roma on loan to have a mixed first season. The attacking midfielder's year was marred with injuries. Still, he produced a decent return of 9 goals and 6 assists in 30 games across all competitions.
This term, the Armenian has been an absolute leader of the Serie A side. The 31-year-old has established himself as a first-team regular. In 17 Serie A games (he was given a starting berth in all of them), Micki has plundered 8 goals and 8 assists. 3 more goal contributions have come from the Europa League as Roma progressed to the knockout stage.
Olivier Giroud (Chelsea, Jan 2018, £18m)
Arsene Wenger generously let the striker go to our rivals to chase his dream of going to the World Cup with France. As we signed Pierre-Emerick Aubameyang that winter, he realised that he needed to seek regular playing time elsewhere.
The move across London turned out to be the right decision as Giroud earned his spot in the national team to claim the World Cup in the summer of 2018.
Next season, he massively contributed to Chelsea's Europa League winning campaign as he became the top scorer of the competition with 11 goals hitting one of them against Arsenal in the final.
In the 2019/20 Premier League campaign, the veteran delivered again. His 8 goals in the last 13 games helped Chelsea qualify for the Champions League.
Aged 34, he's still rated highly by the coaching staff. With Timo Werner struggling to adapt to the new league and Tammy Abraham still to find consistency, the Frenchman is occasionally called upon by Frank Lampard to make a crucial impact as a spearhead. His 9 goals in 16 matches across all competitions tell us that he's yet to say his final word in football.
