The reigning champions of Portugal and Italy go head-to-head at Estadio do Dragao on Wednesday evening, with Porto hosting Juventus as the Champions League returns after winter hibernation.
This last-16 first leg tie sees several old acquaintances reunited in the picturesque port city, all of whom will want to replicate their club's continental form so far, rather than more inconsistent domestic displays.
Nearly two decades since Cristiano Ronaldo left his beloved homeland, Portugal's caps and goalscoring record-holder shows little sign of slowing his prolific strike rate. However, the former Sporting academy graduate has experienced just a single win from six meetings with Porto in his long and distinguished career - registering just one goal too - so will be doubly determined to claim victory this week.
Hired specifically with leading Juventus to continental glory in mind, Ronaldo is seeking to embellish his glittering personal record with a sixth European crown this season and will encounter a long-time teammate and friend - with whom he shared much of that success - on Wednesday.
Porto defender Pepe was by the side of the man he still calls "the best player in the world" as Real Madrid dominated Europe for a prolonged spell in the last decade - also enjoying their nation's finest hour together at Euro 2016 - and will be tasked with the unenviable job of stopping his old friend at Dragao.
Juve's Brazilian full-backs Alex Sandro and Danilo will be assured of a warm welcome too - at least off the pitch - as both played for Porto in the past, both lifting two Liga titles during their time with the Dragons.
Their current side arrive in Iberia without a win in their last two games, however, having failed to hit the net in either. Prior to a Coppa Italia draw with Inter - which was enough to see them through to the final - and subsequent league loss at Napoli, the Bianconeri had embarked on an impressive six-game winning streak, conceding just a single goal in the process.
Undoubtedly, following Andrea Pirlo's experimental and adaptable approach, Juventus are still searching for consistency, but have nonetheless conceded only two goals in their last eight games in all competitions. Currently fourth in Serie A, with a game in hand on leaders Inter, they are certainly live contenders for a 10th successive Scudetto.
A clinical 3-0 victory over Barcelona at Camp Nou in their last Champions League outing was their fourth straight win in the competition. Now competing in the knockout stages for the seventh successive year, Juve are unbeaten in their five previous matches against Wednesday's opponents and approach the tie having finished as winners of Group G.
Perhaps surprisingly, it is not Ronaldo, but Alvaro Morata (on six goals) who is tied at the top of the Champions League scoring charts in 2020-2021. Amid the continuing troubles of Paulo Dybala, both front men are integral to Pirlo's plans of making it to Istanbul in May and bouncing back from exiting the competition at this stage last season, under much-maligned predecessor Maurizio Sarri.
Ahead of their illustrious visitors' arrival in midweek, Porto are yet to concede a goal at home in the Champions League this season - and for 467 minutes in all - a record Pepe and company will be keen to keep intact if they are to progress.
Winning their final match of the group stage at Stadio Georgios Karaiskaki against Olympiakos, the Dragons extended their European unbeaten streak to five, in the club's 24th Champions League campaign - a total fewer than only Real Madrid and Barcelona (both 25).
Porto finished second behind Manchester City in Group C before Christmas, winning four of their six games as they progressed to the knockout phase for the fourth time in a row.
However, currently embroiled in a fascinating tussle at the top of the Primeira Liga, Sergio Conceicao's side have stumbled of late - failing to win in their last four domestic games. That represents a drought by their own sky-high standards, so their coach is under pressure to turn fortunes around with a morale boosting win against the Old Lady - or at the very least secure a goalless draw.
His side currently sit adrift of old rivals Sporting, as they look to retain the league title after fending off Benfica to pick up their 29th domestic crown last season.
Though they have once again shown themselves to be a potent attacking outfit this campaign, with 43 goals so far in the Portuguese top flight, Porto were held to a 2-2 home draw by Boavista on Saturday - their fourth successive stalemate.
A highly eventful encounter saw them come from 2-0 down, miss a penalty to go ahead, then see a potential matchwinner chalked off by VAR. In fact, it was Conceicao's highly-rated son Francisco who won the spot kick and created the disallowed 'goal' - which was followed by a joyous embrace between father and son - only for VAR to cruelly intervene due to a handball.
Nonetheless, Porto's solitary defeat throughout their last 25 league games came in a visit to Sporting in mid-January and they can tackle their toughest assignment of the season with some confidence of snaring a positive result from the rare position as underdogs.
These clubs' most recent meeting was four years ago, at the same stage, with Juventus progressing 3-0 on aggregate on that occasion. This time around, the Portuguese champions may have a better chance of laying a glove on their Italian counterparts.
Porto Champions League form: LWWWDW
Porto form (all competitions): WWDDDD
Juventus Champions League form: WLWWWW
Juventus form (all competitions): WWWWDL
A key cog in Andrea Pirlo's setup, Juventus full-back Juan Cuadrado picked up a muscle injury during Saturday's defeat to Napoli and was replaced during the half-time break, so will be out of action for at least a week. Both returning to their former club, Danilo should start on the right of a back four, with Alex Sandro on the left, given Cuadrado's unavailability.
Arthur, Paulo Dybala and Aaron Ramsey are also likely to miss the trip to Portugal, but influential centre-back Leonardo Bonucci could start on Wednesday after sitting out against Inter and Napoli - alongside either Matthijs de Ligt or long-time defensive partner Giorgio Chiellini.
Growing into his role on the right wing, Federico Chiesa is expected to keep his spot, with Weston McKennie likely to be drafted in for Federico Bernardeschi. Up front, Champions League specialists - of course, to different extents - Alvaro Morata and Cristiano Ronaldo are set to be Pirlo's front pairing.
Home boss Sergio Conceicao has several absentees through injury to deal with, as full-backs Nanu and Zaidu Sanusi have both spent time on the sidelines recently and are joined by midfielder Otavio, who remains out of contention with a muscle injury.
Jesus Corona returned from suspension at the weekend and will keep a starting place in the Porto midfield, alongside Mateus Uribe. Should the Dragons opt for a more conservative 4-4-2, forward Luis Diaz would switch to the left wing, with the clinical pairing of Mehdi Taremi and Moussa Marega leading the line once again - the two forwards have registered a combined 15 goals and 10 assists in the league so far this season.
Porto possible starting lineup:
Marchesin; Manafa, Mbemba, Pepe, Sarr; Corona, Oliviera, Uribe; Diaz, Marega, Taremi.
Juventus possible starting lineup:
Szczesny; Danilo, Bonucci, De Ligt, Alex Sandro; Chiesa, Bentancur, Rabiot, McKennie; Ronaldo, Morata.
Source: Sports Mole / Jonathan O'Shea