By Gabriel TanFollow @@gabetan13
Les Parisiens edged ahead after just ten minutes when Ezequiel Lavezzi blasted a shot past Vicente Guaita following a neat one-two with Javier Pastore, before the latter double their tally just before halftime when he swept home from close range.
But despite their dominance, the visitors were unable to make further headway on the scoreboard and they were made to pay right at the death when Adil Rami poked home a Tino Costa freekick to keep Los Che's hopes of making the quarter-finals alive.
To make matters worse, Zlatan Ibrahimovic received a red card deep into injury-time after he needlessly committed a dangerous challenge on Andres Guardado, and will definitely miss the second leg at the Parc des Princes.
Here, FOX Sports takes a look at where Tuesday's game at the Mestalla was won and lost.
Ultimately, it was individual errors from two players that cost Los Che a two-goal halftime deficit that proved the difference.
On both occasions where PSG scored, Guardado had led his direct opponent - first Lavezzi, then Lucas Moura - get past him too easily, while Guaita could also have done better with either strike.
Valencia coach Ernesto Valverde must be wishing he had a left-footed replica of right-back Joao Pereira to replace Guardado with, especially after the Portuguese's all-action display.
In the heart of defence, Rami actually spent most of the game struggling to keep up with Ibrahimovic, but to his credit, he bombed forward to good effect by netting a late goal.
Guaita - 5 | Pereira - 8 | Rami - 7 | R. Costa - 7 | Guardado - 5
Valverde's three-man midfield started brightly as they strung together a couple of complex passing moves, but it soon emerged that they weren't on par with their opponents.
As the opening 45 wore on, Ever Banega and Dani Parejo both struggled to have any impact on the game, and it was no surprise to see the former hauled off at the break.
Tino Costa was the only one to emerge with any credit as he drove his side forward time and time again, and he nearly pulled one back four minutes from time when his powerful freekick was pushed wide by Salvatore Sirigu.
But four minutes later, his set-piece skills came in handy as he swung in another lovely delivery for Rami to stab home.
T. Costa - 7.5 | Banega (off 46') - 5 | Parejo - 5.5
It was a miserable night for the Los Che attackers as they failed to get any joy out of their battle with the PSG backline.
Jonas, in particular, hardly touched the ball in the 45 minutes that he was on the pitch, while Sofiane Feghouli, who had starred in the group stage, tried his best but failed to make any read inroads down the right.
Instead, the onus was down to Roberto Soldado to pose a threat to the visitors' goal and while he failed to get into any real scoring positions, he worked his socks off and held the ball up well in the final third.
Feghouli (off 84') - 6 | Jonas (off 46') - 4 | Soldado - 7
Given how Jonas and Banega had fared in the first half, it was always going to be easy for halftime substitutes Sergio Canales and Nelson Haedo Valdez to better their efforts.
Canales, in particular, was impressive after coming on and gave the hosts better rhythm in the middle of the park with his range of passing.
Valdez, like Soldado, found himself double-teamed most of the time by Mamadou Sakho and Alex but was presented with an excellent chance in the 76th minute after he snuck in at the near post to meet a Tino Costa cross, only to smash his shot into the sidenetting.
Canales (on 46') - 7 | Valdez (on 46') - 6.5 | Viera (on 84') - N/A
For 89 minutes, the PSG defence had performed their jobs to perfection and looked on track for a deserved clean sheet.
In goal, Sirigu showed clean hands when called upon and made a flying save to keep out Tino Costa's blistering long-range effort, while Alex had headed away everything that was swung into his box.
Sakho was the most impressive of the lot as he nullified the threat of Soldado and made a brilliant challenge midway through the first half to deny the Los Che captain from connecting with a Banega cross six yards out.
Nonetheless, the perfect outing was tarnished right at the death when they went to sleep for a brief moment, allowing Rami to sneak in unmarked and fire past Sirigu from close range.
Christophe Jallet will however be the one player sweating the most over his place in Carlo Ancelotti's starting XI, as he looked the weakest link in the PSG backline. With Netherlands international Gregory van der Wiel waiting in the wings, it remains to be seen if the 29-year-old will play when both sides meet again in Paris in three weeks.
Sirigu - 7 | Jallet - 6 | Alex - 6.5 | Sakho - 7.5 | Maxwell - 7
It will take a while before Lucas repays the €45million that PSG reportedly paid Sao Paulo for his services, but based on Tuesday's display, it looks as though he will be worth every cent, and not just because of the assist he laid on for Pastore's goal.
The 20-year-old was unstoppable down the right and gave Guardado a real headache, and far from being just a pace merchant, he also showed he has the end product to his game, and was unlucky not to score in the 9th minute when his ferocious shot came back off the post.
His fellow youngster Marco Verratti some time to get going but once he found his groove, he never gave his opponents time to settle and also got in their faces, while being neat in possession at the same time.
Likewise, Blaise Matuidi performed his task to perfection, forming a shield in front of his backline and snapping at every Valencia player who received the ball on the edge of the PSG box.
In terms of overall contribution, Pastore was perhaps the most disappointing of the lot as he failed to impose himself on the game, but when he decided to turn it on his touches were of pure quality, and it was no surprise he walked off the Mestalla pitch with a goal and an assist to his name.
Lucas (off 53') - 8 | Matuidi - 7.5 | Verratti - 7 | Pastore (off 88') - 8
In Ibrahimovic and Lavezzi, PSG have a strike duo that could give problems to any defence in the world.
Both players are excellent in holding up possession but are equally devastating when running directly at goal, and showed an almost-telepathic understanding with some of their passing.
Lavezzi's opener was also a strike of pure quality as it whizzed past a dumbstruck Guaita, but Ibrahimovic ended the game as the villain after losing his cool and committing a dangerous challenge on Guardado.
Ibrahimovic - 6.5 | Lavezzi (off 76') - 8.5
Although he's yet to establish himself as a key member since coming through the ranks, it's easy to see why Clement Chantome is a fan favourite with the PSG faithful.
The 25-year-old never stopped running after coming on for Lucas and was unlucky not to lay on an assist for Ibrahimovic with a clever back-heel.
Apart from Chantome, Jeremy Menez and Sylvain Armand both also came on for the visitors but had minimal time to make an impact.
Chantome (on 53') - 7 | Menez (on 76') - N/A | Armand (on 88') - N/A