#3 Sell - Laurent Koscielny
A terrible knee injury for captain Kos against Atletico Madrid last season sidelined him for more than a year. Laurent, at the age of 32, experienced a career-ending injury and was not expected to make an appearance in an Arsenal shirt since then. However, he came through it like a true warrior and played a key part for the Gunners this season.
Though Arsenal's defence was unarguably the worst in the top six, with Koscielny and Sokratis, Arsenal looked pretty decent at the back. The likes of Kolasinac and Ainsley Maitland Niles are not natural fullbacks as they prefer playing in a wing-back role, and therefore, while playing a back four, Koscielny and Sokratis had to take all the pressure on themselves due to the unfortunate injury to Hector Bellerin and Rob Holding.
Laurent Koscielny certainly made Arsenal's defence 10 times better, but his age and injury concerns have to be taken into consideration. Reportedly, Borrusia Dortmund are interested in the Frenchman's services and Arsenal would let go of their captain if the German giants can meet his valuation of £10 million.