#2 Ousmane Dembélé
This one is undoubtedly the most surprising on this list, given just how much Barcelona were prepared to splash on the former Rennes and Borussia Dortmund winger so early into his professional career.
Ousmane Dembélé, 20, signed a five-year contract with the La Liga leaders after they'd agreed an eye-watering £96.8m fee (plus £35m in add-ons) last summer.
The talented Frenchman's progress has stalled somewhat after sustaining lengthy spells out on the sidelines following muscular (hamstring and thigh) injuries.
He scored his first goal during their 3-0 win over Chelsea in the Champions League last-16 earlier this month and speculation suggests he'd be interested in the possibility of a reunion alongside close friend Pierre-Emerick Aubameyang in north London - the pair were previously a lethal duo in the final third for Dortmund.
It's highly unlikely that Barcelona would even consider parting ways with Dembélé at such a pivotal stage in his development, not least given how much they spent to capture his services. However, the versatile winger is the type of player that Arsenal must target if they are to improve over time in future.