Here, the PA news agency examines the key talking points ahead of the Seville showdown.
Can Chelsea shut out the outside noise
Thomas Tuchel has told his Chelsea players to ignore the bigger picture this week, and let everyone else "wreck their heads" over the Blues' chances of ending this season with silverware. The truth is that this week will define Chelsea's season in one respect, given the cup matches against both Porto and Manchester City. As Tuchel said on Monday, Chelsea are determined to end the week still competing in the Premier League, the Champions League and the FA Cup. And the German manager insists the only way to do that is to focus on one job at a time.
The Blues will need their "emotional leaders" more than ever
Tuchel revealed Kai Havertz is not one of the Blues' "emotional leaders" after Saturday's 4-1 thrashing of Crystal Palace. So when asked who set the mental tone in the Chelsea dressing room, Tuchel picked out Toni Rudiger, Cesar Azpilicueta and Mateo Kovacic. Now those three players will need to drive the Stamford Bridge men forward in a testing battle against stubborn Porto.
Chelsea sweating on N'Golo Kante
France midfielder N'Golo Kante has hit back to his very best under new Blues boss Tuchel, restored to the base of midfield and to his all-action linchpin role. The World Cup-winner may not be fit enough to start on Tuesday however, as he continues to shake off his latest hamstring problem. Tuchel will leave it until the last minute to see whether Kante can feature from the start, but will always have one eye on Saturday's FA Cup semi-final with Manchester City. Kante can be expected to feature in both matches, but perhaps not for two sets of 90 minutes, or more.
Porto determined to stick to their guns
Porto's pre-match press conference was dominated by a return to one central theme. Playing "the Porto way" revolves around attitude and endeavour rather than tactics, with the Dragao Stadium men determined to channel the club's proud history in order to pull off a major reversal of fortunes in this tie. Boss Sergio Conceicao gave short shrift to the idea of Porto just lumping all their attacking players into the starting XI, saying: "I'll answer in a very simple way, and be very assertive: it's not with lots of forward players that we attack more or with more defenders that we defend better."