Chelsea will remember last season
The embarrassing exit at the hands of Paris Saint-Germain last season still hurts Chelsea and their fans. After picking up a vital away goal and a decent draw in the Parc des Princes, the Blues were confident that they'd be able to progress past Laurent Blanc's team on home soil.
The task only seemed to get that much when Zlatan Ibrahimovic was very harshly sent off for a tackle on Oscar. Chelsea had an hour to play against 10-men - they could've held on for a 0-0 draw and would've gone through. What followed was one of the biggest bottle jobs of the Roman Abramovich era, even if they should have had a penalty.
Chelsea scored a late goal through Gary Cahill to take a 2-1 aggregate lead but then allowed David Luiz to equalise. It went to extra-time. Another half an hour against a team that had already been playing a man short for 60 minutes. An Eden Hazard penalty put Chelsea ahead again and Jose Mourinho's team only needed to see out the final 15 minutes. They couldn't and crashed out of the competition after being overwhelmed by the Parisiens.
It was a truly awful defeat and one that the Chelsea players, the majority of whom are still at the club, will want to avoid.
Chelsea under Hiddink
Under interim manager Guus Hiddink, Chelsea have got used to not losing. His only defeat in 16 games in his second spell at the club was that 2-1 defeat in Paris a couple of weeks ago. In his tenure he has faced Manchester United twice and Arsenal, coming away with credible results in all of them.
Across his two spells Hiddink has never tasted defeat at Stamford Bridge, winning four of his nine matches this season and six of his nine matches in his first spell. His combined record is 10 wins and seven draws at Stamford Bridge - those include the impressive 1-0 win over Juventus, the thrilling 4-4 Champions League 4-4 draw with Liverpool and the controversial 1-1 semi-final draw with Barcelona.
Chelsea really have to win tonight, but they can be confident that in Hiddink they have a manager who doesn't often lose.
PSG are off colour
Blanc's team may well be racing away with Ligue 1 (they are an embarrassing 23 points ahead of closest team Monaco) but they have just suffered a minor blip in recent weeks.
It's very minor in truth, one win in three or three of their last six, but for a team that rattled off 17 straight victories earlier this season and were undefeated in more than 30 matches, it's certainly something.
Zlatan Ibrahimovic hasn't scored in his last two and was rested against Montpellier.
Clutching at straws with this one maybe...
PSG lack experience
A bigger motivating factor for Chelsea should be that they are a side with bags and bags of European experience. Multiple players from the 2012 Champions League and 2013 Europa League winning sides are still at Stamford Bridge, while they reached the semi in the season before last.
PSG proved last season that they are not going to be overwhelmed by playing Chelsea, but this is still a team (and a manager) that for the most part is unproven in Europe's later stages. Influential players, leaders in the dressing room like Zlatan Ibrahimovic and Thiago Silva have never won the competition, although the side is probably better than it was last season.
Laurent Blanc hasn't got past the quarter-final stage despite the vast riches at his disposal, something of an under-achievement.
Their engine room is in need of a service
Two of Paris Saint-Germain's most important and influential players could be missing at Stamford Bridge. Midfielders Blaise Matuidi and Marco Verratti have struggled for fitness in recent weeks and although it would be a huge surprise to see them both out, that doesn't mean either will be operating at anything like 100 per cent.
When at their best the ferocious pair overwhelm opposition midfielders with their hyper-aggressive pressing and, frankly in Verratti's case, frequent fouling, that disrupts the opposition's flow.
Verratti has only played 45 minutes since the team's last met and Matuidi only in two brief substitute appearances. A large part of that was to give them the best possible chance to start against the Blues, but even if they do play it's not as if they will be at their very best.
Should either miss out, then Blanc's next best options for central midfield should both hand Chelsea an advantage. Adrien Rabiot is an extremely talented prospect, but he is an inexperienced 20-year-old. Javier Pastore is an explosive attacker, but does not have the discipline to play regularly in central midfield.