The time has arrived: the biggest game of Arsenal’s season. Considering the Gunners have competed in a domestic final in the guise of the league cup this season, this may seem like a brash statement, but the stakes are so much higher in this second leg of the Europa League semi-final against Atletico Madrid.Not only does the result of the match determine whether Arsene Wenger’s side will be contesting the final, it also decides whether the Champions League dream is still alive for next season. When Wenger announced he would be departing Arsenal after 22 years at the close of the season, everybody’s thoughts went to winning the Europa League and claiming one final success as the manager of the team he had seen such glory with in the past – but with Diego Simeone’s side between him and the final, it was never going to be easy.The scores are tied at 1-1 from the Emirates leg; maybe a few months ago this wouldn’t have looked as egregious of position, but things have changed. Arsenal have the worst away form of any team in England’s top 4 leagues, having gained no points on the road in 2018. In Europe things have been a little bit better, if not amazing. Perhaps Arsenal’s result of the season came in the 2-0 dismantling of AC Milan at the San Siro, which proceeded a fine 3-0 victory over Ostersund in Sweden. The most recent away European game wasn’t as positive – despite a 4-1 lead from the first leg, after falling two goals behind in Moscow, things were a little shaky, only to be redeemed in the latter stages of the game with two goals in repose.Before getting onto the numbers that suggest Arsenal likely won’t win this match, it’s worth looking at how the game at the Wanda Metropolitano could go down.If Arsenal win the game 1-0, then they’re in the Europa League final. If the game is drawn 1-1, it will go to extra-time. With this being the case, if Atletico score, Arsenal need a goal due to the away goal conceded in the first leg. If the game is a 2-2 draw, then Arsenal will progress due to away goals…… now, why does that seem unlikely? Well, because as mentioned, Arsenal have the worst away record in English football this calendar year and Madrid are one of the most defensively resolute teams in the world – only 3 goals at home conceded in 2018 - winning due to away goals really does seem like an unlikely option!As those watching last Thursday seen first-hand, Madrid aren’t an easy side to break down. After just 12 minutes, Atletico had lost their left full-back to a red card and their manager to a tantrum. It was as close to the worst possible start to the away leg of a semi-final as a team as well set up as Madrid could have envisioned.But that wasn’t to be the case. A quite frankly remarkable display from goal keeper Jan Oblak and a terrific adaptation to playing with 10 men for the rest of the squad seen Atleti make it to the hour mark at nil-nil despite a genuinely good Arsenal performance.Then, Alexandre Lacazette broke the deadlock, and it looked like things may be opening up. At one goal to the good, it looked like when Arsenal would score next and how good their lead would be going into the semi-final rather than any alternative.But then, as we all know, there was a lapse – a singular lapse – in concentration, and Antoine Griezmann punished the defence to make it 1-1. In one regard, one could say the Spaniards deserved it – a pay-off for their resilience. In another, it was disastrous – the home leg was where an advantage needed to be cultivated with the knowledge of Simeone’s sides capability on home turf.Regardless, this second leg has arrived, and it’s not going to be easy. The game is Wenger’s 250th European game as Arsenal manger. Speaking before the game, he talked of his optimistic targets:“The target is to get to 251 European games but I believe we come to a place which has a good history in Europe. We know exactly what to do, and how we have to behave, and that is an advantage sometimes”, sensible, encouraging talk from the manager in what must be an intimidating circumstance.If Arsenal are to cause damage against Madrid’s exceptional defence, they will need their goal scorer from the first leg to be on-form. Lacazette has had a part to play in 13 goals in his past 13 Europa League starts – 11 goals, 2 assists.He’ll have assistance in this leg from Henrikh Mkhitaryan who missed the first leg with a knee injury, but both played and scored in the loss against Manchester united at the weekend, so will hope to continue his stellar Europa league form since joining the club in January.Mohamed Elneny is still out, Alex Iwobi has travelled although has a slight hamstring strain and Pierre-Emerick Aubameyang is unfortunately cup-tied.Returning for the opposition is former Chelsea striker Diego Costa, who missed the previous leg with a hamstring injury. From his time in England, supporters will know the enormous threat he poses when on-form, and this is only exacerbated when playing beside the talent of Griezmann. Another former Chelsea man – Felipe Luis – has been included in the squad and may play, but is unexpected to be able to complete a full 90 minutes as he recovers from a leg-break.It’s a game that will influence both legacy and the future. Wenger has the opportunity to bow out in glory if he can get his hands on the Europa League trophy in his final match as manager of the club, and in doing so, put the club in a good position for whoever it is that takes over. If he pulls off a win against Simeone’s side, he deserves all the plaudits he gets. Arsenal play Atletico Madrid at the Wanda Metropolitano in the second leg of their Europa League Semi-Fianls on Thursday the 3rd of May, with kick-off scheduled for 8.05pm.