A heavyweight clash if only in terms of lavish spending, both clubs might be relieved that a defeat at this juncture would not be fatal for their prospects of progression.
As much as Galatasaray and Club Brugge will be willing underdogs, this is likely to be the toughest test PSG and Madrid face in the group stages. Accommodating a legion of talents and egos, this would be a compelling, glamorous fixture at any stage of the season.
There is unfinished business and a desperation to avoid familiar dejection in PSG's latest Champions League campaign, not least because of the nature of their exit last season.
2-0 up after the first leg at Old Trafford and heavy favourites to go through against an unproven United side, PSG slumped out with a 3-1 defeat at the Parc des Princes sealed by a last-gasp penalty for the visitors.
That was the third successive season in which the French champions have tumbled at the round-of-16 stage, representing a poor return for a club whose vast outlay has repeatedly eclipsed their achievements in Europe.
In attack, Neymar and Kylian Mbappe alone joined for fees totalling more than £363 million, justifying expectations that the pair might provide the goals that could finally take PSG into the quarter-finals and beyond.
They suffered an early shock in Ligue 1 this season when they lost 2-1 at Rennes, but are now in their usual position at the top of the table having won four of their first five games.
Having brushed Nimes aside 3-0 in their first home match, they followed up that defeat by taking 50 minutes to find a breakthrough against Toulouse in Paris, eventually winning 4-0 with the help of a Eric Maxim Choupo-Moting double.
PSG established a two-point lead at the top of the table in the most marginal of fashions on Saturday, beating lowly visitors Strasbourg with a 92nd-minute Neymar goal.
Recent form: WLWWW
Exiting to the despair of their home fans at the round of 16 stage, Madrid's Champions League exit played out in just as disastrous fashion as PSG's last season.
Returning to the Bernabeu with a 2-1 lead from the first leg in Amsterdam, Zinedine Zidane watched his side capitulate against Ajax's young pretenders, who spared them the agony of a late defeat by surging into a 3-0 lead.
Ajax finished 4-1 winners on the night, causing significant soul-searching for Madrid on an occasion encapsulated by Nacho's last-gasp red card.
These are strangely unsure times for Real, who have won two of their opening four La Liga matches, as well as experiencing apparent disciplinary issues.
Valladolid denied them three points with an 88th-minute equaliser to cancel out Karim Benzema's late opener, and they were twice behind at Villarreal before grabbing a 2-2 draw.
Gareth Bale, whose future made for soap opera material during the summer, scored on the stroke of half time and four minutes before the end of normal time to save a point.
The current Wales captain was then sent off in the 94th minute, emulating the dismissal of playmaker Luka Modric during the 3-1 win at Celta Vigo on the first day of the season.
Real Madrid are third in the table - two points behind leaders Sevilla - after a 3-2 win at home to Levante on Saturday.
They dominated the match and were 3-0 up after 40 minutes through two opening goals by Benzema and a third from Casemiro, only for Levante to hit back after the break.
Recent form: WDDW
At one point this summer, Neymar looked certain to leave Paris for the probable destination of Barcelona - and the disruption that caused, together with injury problems, meant his injury time winner against Strasbourg came at the end of his first game of the season.
The Brazil striker returned for his country with recent appearances against Colombia and Peru, but was booed by his club's fans at the Parc des Princes before proving their salvation with his last-gasp overhead kick to seal the three points.
He had been included to fill a void in attack left by Kylian Mbappe's thigh tear and Edinson Cavani's hip problem, with both strikers expected to be unavailable until late September at the earliest.
Neymar cannot continue his scoring exploits against Madrid, having picked up a three-match ban for questioning the integrity of the referee in the aftermath of that loss to Manchester United in PSG's last Champions League game.
To the joy of his fans on social media, Mbappe disclosed news of an early return to training last week, but the lightning-heeled 20-year-old will not be ready to test the Madrid defence.
Real Madrid were back in training on Sunday, although Eden Hazard - a debutant the previous evening - is not in the running to play against PSG, according to Zidane.
The Madrid coach says he will not be returning to France with his most high-profile of the summer in tow, as Hazard has not reached full fitness following a spell on the sidelines.
Midfielder Isco, who has been out with a thigh injury, also trained, but will not be ready for Wednesday as he continues the final phase of his recovery.
Left-back Marcelo is Zidane's latest injury victim, having been ruled out of the match with a spinal injury announced by the club on Monday.
Playmaker Luka Modric and midfielder Federico Valverde will not be ready for PSG, and winger Marco Asensio has a long-term knee injury that will keep him out until next year.
Paris Saint-Germain possible starting lineup:
Navas; Meunier, Silva, Diallo, Kurzawa; Verratti, Gueye, Di Maria, Icardi, Sarabia; Choupo-Moting
Real Madrid possible starting lineup:
Courtois; Carvajal, Varane, Eder Militao, Mendy; Casemiro, Rodriguez, Kroos; Vazquez, Junior; Benzema
Head To Head
Real Madrid have a slight edge in the previous meetings between these sides, recording four wins to PSG's three.
Most recently, the Spaniards won 2-1 in Paris to cap a 5-2 aggregate victory in the round of 16 in 2018, when Cristiano Ronaldo scored the opener and Cavani scored late to give PSG a glimmer of hope in the tie, swiftly extinguished by a Casemiro goal 10 minutes from time.
Madrid had come from behind to win 3-1 in the first leg, including two Ronaldo goals.
They met twice in the group stage in 2015, sharing a goalless draw in Paris before Nacho's first-half winner gave the hosts three points in Madrid the following month.
We say: Paris Saint-Germain 1-1 Real Madrid
This is a treat to start the first week of the Champions League group stages, as well as being tough to call in light of the unspectacular starts made by both sides to their league seasons.
The players who are not involved are likely to be more noticeable than many who are. Mbappe and Neymar are significant losses from PSG's forward line, and the creativity of Hazard and Modric will be missed by Madrid.
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