Three key talking points as Chelsea host Paris St-Germain in the Champions League

This should be the tie of the round.

Chelsea and Paris St-Germain meet at Stamford Bridge on Wednesday with the last-16 UEFA Champions League tie perfectly poised after the first leg in the French capital three weeks ago. Whereas both Arsenal and Manchester City's first-leg results effectively decided their respective ties, Chelsea's invaluable away goal in that 2-1 defeat means it's all to play for in what is undoubtedly their biggest game of a disappointing - if improving - season. PSG have the league wrapped up in France, so the true test of their progress will come in Europe's top club competition. It's not too much of an exaggeration to say both teams' seasons are on the line. Here's three talking points ahead of the game:

1. This is the true test of Hiddink's quiet revolution

In addition to the dark cloud lifting from Stamford Bridge when Jose Mourinho left Chelsea back in December, media and public attention seems to have departed with the "Special One". Away from the bright lights of Broadway (and Leicester) Chelsea are, however, the form Premier League team in 2016, and their interim manager has broken the record for longest unbeaten run for any new manager in the division. Guus Hiddink has yet to taste defeat in the league during his 12 games in charge, with his only defeat coming away to PSG in the first leg. However, even that loss isn't the bad result it may seem. In 48.9% of Champions League ties when the away team lost the first leg 2-1, they advanced to the next stage. This is the third time PSG and Chelsea have met in the UEFA Champions League knock-out rounds, and it could be argued that this fixture last season was when the flaws in Mourinho's tactics became evident. The first-leg had ended 1-1 in Paris, and after Zlatan Ibrahimovic was sent-off 30 minutes into the second-leg, progression to the next round seem all but certain for the Premier League team. However, Mourinho's restrictive tactics meant Chelsea weren't equipped to break down their opponents, and despite taking the lead through Gary Cahill, and playing 90 minutes with an extra player at home, they drew the game 2-2 and went out on away goals after extra-time. Chelsea had just 35% of possession in the game two weeks ago, but with PSG protecting a lead, the emphasis will be on the home side to break down their opponents. He may have rejuvenated the squad after the suffocating final months of Mourinho, but this will be the true test of Hiddink and Chelsea's recent progress.

2. Will Diego Costa be the key man?

Diego Costa was badly missed during Chelsea's draw with Stoke City on Saturday. The striker, who was suffering from a minor tendon injury, was rested for the fixture, but is expected to return on Wednesday evening. Costa's stand-in Bertrand Traore scored against the Potters, but the 20 year old only managed three touches in the opposition penalty area. Costa managed just six goals before Hiddink's arrival, but he has since scored eight goals and, according to football statistical website Whoscored.com, averaged a performance score of 7.41 per game over his last six appearances. Costa's Champions League goal return for Chelsea has, however, been something of an anomaly in the context of his time at Stamford Bridge. Despite scoring 35 goals in 71 games for the Blues, just one of those has come in Europe in 13 appearances. Like his interim manager, Wednesday's game will be the true test of Costa's revival. However, even if he doesn't find the net, his world class wind-up skills could get under the skin of the erratic David Luiz. Either way, Costa is sure to be at the centre of the action.

3. This is Zlatan's last chance to shine in England

Zlatan Ibrahimovic found the net in the first-leg against Chelsea, but strangely has scored as many goals (four) in one game against the English national team, as he has in 19 games against English clubs. The Swedish striker is now 34 years old, and seemingly in the final months of his spell with PSG, so this could be potentially his final UEFA Champions League game. He may have won 12 league titles in the past 14 years, but for a player of such undoubted talent, and confidence, the failure to win club football's biggest prize will remain a sticking point when assessing his career. https://www.youtube.com/watch?v=t2qcRNSNQ1Q In fact, Zlatan's Champions League career could be easily be used as evidence that the striker is something of a flat track bully. In 37 knock-out UEFA Champions League games, Ibrahimovic has scored just eight goals. However, in 79 group games he's found the net 38 times. The English football public seem to be one of the few who remain unconvinced by the Swede, not that he'll care about that. But he does have the chance to prove he truly is a big game player, and silence his doubters, against Chelsea. If not, it could be the last we see of Zlatan in the Champions League. PepsiCo has kicked off the next phase of its UEFA Champions League sponsorship with a new on-pack promotion that gives you the chance to win prizes every hour with #GAMEREADY Doritos packs.

Prizes include official UEFA t-shirts and footballs to tickets to the quarter-finals, semi-finals and the final in Milan on May 28th.