Real Madrid against Paris Saint-Germain looks the glamour tie; Chelsea's clash with Barcelona is the meeting of two recent winners. Yet the Champions League's round of 16 only features one contest with two former champions who have a combined seven triumphs in the most prestigious club competition of all.
Porto's meeting with Liverpool pits two-time conquerors of the continent against the club whose fans boast of winning "it" five times; the 2004 victors against their 2005 counterparts. If that feels like a different era, it is because it was: a time when Jose Mourinho and Rafa Benitez represented the future -- their cautious, counter-attacking blueprints capturing the zeitgeist as professional coaches outwitted the distinguished ex-players in other dugouts.
It is because, together with Chelsea's improbable victory in 2012, they rank as the most unlikely Champions League wins of the 21st Century. That sense has been rubber-stamped by their subsequent fortunes. While Porto at least had a steady stream of Portuguese titles until 2013, Liverpool have only secured two trophies since 2005. Both Champions League wins left wonderful memories, but no legacy in terms of sustained success in Europe. Neither started a dynasty.
If it could be branded a missed opportunity, the ultra-ambitious Benitez may endorse that argument. His Liverpool came closer than Porto to staging a repeat, reaching the final again in 2007 and topping UEFA's club rankings, which are compiled over a five-year period, when they beat Real Madrid 4-0 in 2009. Extra spending might have propelled them to another European Cup, but the fact is that Liverpool exited in the round of 16 as defending champions; so, 12 months earlier, had Porto.
From being officially Europe's best team in successive seasons, they could be deemed arguably its premier selling clubs -- immediately, in Porto's case, and from 2009 for Liverpool.
A CIES Observatory report in 2016 showed the Merseysiders had made the most money from player sales in the previous 14 transfer windows, and all that was before Philippe Coutinho joined Barcelona for £142 million. Porto ranked fifth, but perhaps only one lucrative sale from second place.
Since 2009, Liverpool have had six major departures, either to England's moneyed challengers or Spain's dominant duo: Xabi Alonso, Javier Mascherano, Fernando Torres, Luis Suarez, Raheem Sterling and now Coutinho. Include add-ons and their fees amount to £366m.
There has been a constant traffic of players from Porto, excellent importers showing their negotiating skills to command premium prices for both high-calibre players -- such as James Rodriguez, Radamel Falcao, Ricardo Carvalho, Pepe and Hulk -- and those who feel hugely overpriced: Eliaquim Mangala, Jackson Martinez, Andre Silva, Danilo, Giannelli Imbula and Jose Bosingwa.
If Porto's is an economic model, Liverpool's perhaps temporary transformation into a deluxe feeder club was more enforced by the ownership of Tom Hicks and George Gillett and consequences that outlasted their ousting. The loss of pivotal performers can explain why Porto have only been quarterfinalists twice and never semifinalists since 2004, while Liverpool are in the round of 16 for the first time in nine seasons.
Neither built on glory. In 2005, Liverpool brought in Pepe Reina, Peter Crouch, Momo Sissoko, Boudewijn Zenden and Mark Gonzalez. The first three, to varying degrees, justified their purchases but there was no statement signing, no superstar to elevate a winning team.
Likewise, in 2004, Porto recruited Pepe, Ricardo Quaresma and Raul Meireles (who eventually came good) and Luis Fabiano and Diego, who failed. But they had already been weakened by the immediate loss of Paulo Ferreira, Carvalho, Deco and, most crucially, Mourinho, whose move to Chelsea was agreed even before the final win over Monaco and whose successor, Luigi Delneri, never took charge of a competitive game.
Mourinho's side broke up with Maniche, Costinha and Derlei leaving the following year. Porto became just another team, albeit in a football factory with a profitable business model, at alarming speed.
Liverpool also discovered the perils of success and the feeling that everything is transitory. Steven Gerrard was almost lured to Chelsea by Mourinho in 2005; Vladimir Smicer's departure was ratified before he scored in Istanbul; Benitez had to spend some of the summer persuading the catalytic substitute Dietmar Hamann to stay. With apologies to Mascherano, who was on the bench at West Ham, the manager did not make another marquee signing until after the 2007 final defeat: Torres.
If it is often tempting to wonder what might have been when revisiting Benitez's Anfield years. The long list of missed targets in his six-year reign included future Champions League winners such as David Villa, Dani Alves and Nemanja Vidic.
But to look back is also to marvel. Porto are the only champions from outside Europe's top four leagues since Ajax in 1995; Liverpool are the only ones who finished 37 points adrift of the winners of their domestic division.
Perhaps there was a vacuum, with no truly dominant team on the continent between the time when Real Madrid's Galactico project started to implode and when Barcelona and Manchester United advanced. The best team in Europe in 2003-04 may have been Arsenal's Invincibles and the finest in 2004-05 was perhaps Mourinho's Chelsea, but a knockout structure allowed tactically-excellent underdogs to seize their moment.
Yet more than a decade later, that is still what it was: one magnificent moment for each; an isolated, extraordinary triumph that never led to anything as impressive again.