Much has changed in this season's Champions League, the knockout play-off phase being one major new introduction

Arsenal sit fifth in the Champions League table heading into tonight’s action, having won four of their opening six games. They drew with Europa League holders Atalanta and lost to Inter Milan but have otherwise impressed, with the 5-1 win away at Sporting CP surely their standout performance.

It's been a journey into the unknown, but the new-look Champions League is finally reaching the climax of the league phase. Here's what's needed to go through.