#1 Not giving in to pressure at 0-2
With Arsenal, the story of wilting under pressure is not uncommon. The team has gone on to lose games from extremely strong positions in the past and has the tendency to crumble under coercion from a spirited, low-key opposition.
Hence, when CSKA Moscow grabbed their goals in the game, it seemed all too plausible for the Gunners to lose their footing and throw away a European knock-out tie once again. The fact that Barcelona fell to a similar fate last week in the Champions League must've also played on the minds of the Arsenal players.
However, after Chambers came on to the middle and Mohammad Elneny started playing deeper to protect the defence, the visitors seemed to regain their composure. Welbeck's goal eased the tension even further and all but secured Arsenal's place in the last four of the Europa League.