Arsenal boss Arsène Wenger has one last shot at European glory with the Gunners, after confirming that he will be leaving the club at the end of the season.
The aggregate score is currently 1-1 as Arsenal travel to Atlético Madrid's Wanda Metropolitano Stadium for the second leg on Thursday.
Below is a look at the best possible XI that Wenger could field as his side look to book their place in the Europa League.
David Ospina looks set to continue his run as Arsène Wenger's preferred cup goalkeeper for this semi final second leg.
Experienced internationals Shkodran Mustafi and Laurent Koscielny look to make up the central core of Arsenal's back four as they look to deal with the threat posed by Diego Costa and Antoine Griezmann.
Attacking full backs Hector Bellerín and Nacho Monreal look set to take their places either side of them.
Arsène Wenger looks likely to deploy Granit Xhaka, Jack Wilshere and Aaron Ramsey as a central midfield three, with Henrikh Mkhitaryan and Mesut Özil both occupying number 10 roles ahead of them.
This central solidity will allow Hector Bellerín and Nacho Monreal to push higher up the pitch during attacking phases of play.
Former Lyon striker Alexandre Lacazette looks set to line up as a lone striker, although will not be starved of service as the full backs push forward and he receives support from Mkhitaryan and Özil in the two number 10 roles behind him.
The Frenchman has scored 16 goals in 36 games since joining Arsenal last summer.