The last four teams standing return to play in the UEFA Champions League this week for the first leg of the semifinals, when some of Europe's top sides will begin to map out their route to the final on May 31 at Munich's Allianz Arena.

Arsenal hosts PSG on Tuesday in the first leg of their Champions League semifinal at the Emirates. The Gunners return to this stage for the first time since 2009 after knocking out defending champions Real Madrid with a 5-1 aggregate win. PSG took down Liverpool and Aston Villa to reach their fourth semifinal in five years.

Anyone in the UEFA Champions League semifinals can win it. Here's why Arsenal, PSG, Barcelona and Inter Milan will (and why they won't) win it.