The Champions League returns next week with the first set of the Round of 16 matches. The marquee matches might be Real Madrid vs Paris Saint Germain and Chelsea vs Barcelona, but there are quite a few ties where underdogs can announce their intentions.
Basel will hope to conjure some magic when they take on heavy favourites Manchester City, Besiktas will also start as outsiders - despite finishing the group stages undefeated - when they take on German giants Bayern Munich.
The first knock-out stage has traditionally been the moments when giant-killers make their presence felt and this article takes a look at the five greatest Champions League upsets in the Round of 16 over the years.
5. PSV Eindhoven 2 - 1 Arsenal: 2006-07
The mid-2000s saw English clubs dominating the UEFA Champions League. Fresh from the 2005-06 campaign where they went all the way to the final, Arsenal were considered to be one of the favourites for the title the ensuing year. That didn't go quite according to plan.
Three English teams would make the semifinals that year, but Arsenal would be dumped out in the first knockout stage by Dutch side PSV Eindhoven. Despite having a better European pedigree than Arsenal, PSV's victory was considered a major upset.
In the first leg, the Arsenal side comprising of Thierry Henry, William Gallas and Freddie Ljungberg dominated the proceedings at the Philips Stadion till half-time - but Ronald Koeman's PSV changed the tide after the break. Edison Mendez beat Jens Lehmann to give the hosts a 1-0 advantage to take to London.
Needing two goals to go through at Highbury, Arsenal suffered a setback before the match as Henry was relegated to the substitute's bench following a foot injury. It was PSV's turn to dominate the first half this time as Arsenal looked increasingly rattled.
The Gunners did receive a stroke of luck when PSV defender Alex diverted a corner into his own net in the 58th minute. The tie was level on aggregate and Arsenal turned the heat on, replacing Julio Baptista with Henry for the final 25 minutes.
Though, it was PSV who struck the fatal blow when Alex redeemed himself with a fine header from Mendez's free kick to beat Lehmann in the 83rd minute. PSV held on for the rest of normal time and injury time to progress to the quarter-finals 2-1 on aggregate at Arsenal's expense.