Marseille managed to take a point in Le Classique with Saliba the star of the show, with the frozen-out Gunner celebrating wildly after making an incredible last man goal-saving tackle to deny Mbappe.
Saliba was signed by Arsenal in 2019, joining on a £27million deal from Saint Etienne before being loaned straight back to the French side, and much was expected of the highly-rated youngster when he eventually moved to north London.
The 20-year-old finally rocked up at the Emirates last summer to train with the Gunners ahead of the 2020/21 season, but Mikel Arteta wasn't impressed by the centre-back and sent him back out on loan to Nice.
Instead, Arteta signed Gabriel Magalhaes to fill his spot in the back-four.
The story was again the same this summer, with Saliba sent to on his third loan spell of his Arsenal career, to Marseille, as Arteta purchased Ben White from Brighton for £50m and was promptly given Saliba's No.4 shirt.
In almost two and a half years as an Arsenal player, Saliba is yet to play a single minute for his parent club.
But it appears one of the only people in the game who doesn't rate Saliba is Gunners boss Arteta, with his judgement now being questioned after the centre-back's fine start in the south of France, dominating what many consider one the best forward lines in the game.
Marseille manager Jorge Sampaoli has had incredibly high praise for Saliba since his arrival at the club, with the 20-year-old one of the first names on his team sheet.
"He's a top player at his position," Sampaoli said.
"We were lucky to get him on loan, it wasn't simple. He's great at marking, but good bringing the ball out too.
"He's a future great of French football, he's very good at starting plays."
Saliba has reciprocated the praise from his new manager, while explaining why Marseille were the perfect fit to continue his development.
"With [Jorge] Sampaoli, we have to give it our all from start to finish," Saliba explained.
"We can't do things halfheartedly. Sometimes I don't put enough power on my passes and he tells me: 'Those are kids' passes!'
"[Marseille club president Pablo] Longoria told me that if I wanted to reach the next level in my progression, I had to come here.
"If you can perform at Marseille, to play under this pressure, you can play anywhere else.
"I hadn't even signed yet and I was already getting messages from supporters. I've never seen passion like this, in this town the only thing that matters is OM!"
The Frenchman has averaged an impressive 94.5% passing accuracy across all his games this season and was again in excellent form against PSG, stopping the financial behemoths from running away at the top of Ligue 1.
He was also joined by fellow Arsenal loanee Matteo Guendouzi in the Marseille line up, who has been so good since returning to Ligue 1 that he's earned a call up to the French national team.
And the Arsenal loanees earned praise from French publication L'Equipe, who are notoriously hard to please, with both players give a game-high rating of seven. In comparison, Lionel Messi was given a four and Neymar a dismal three.
Arteta's handling of Saliba has been questioned by Loic Perrin, who played alongside Saliba at Saint-Etienne and says he deserves a chance in the Premier League.
"I don't understand how they didn't even try him at least once," said the now retired centre-back.
"In one-on-one situations, he's got extraordinary footing and always gets out of it.
"Furthermore, he's a great kid to have in a group. At Nice, after many months without playing, he was good immediately when Nice were in bad form.
"At Marseille, in a crazy atmosphere, same thing. He doesn't get carried away. He could have given something to Arsenal."
"He's a top player at his position," he said.
Saliba is yet to make an appearance for France's first team which is stacked with high-end talent, but he's appeared all the way up from U16s to U21s.
One of his coaches from the France youth set up, Jean-Luc Vannuchi, has similarly heaped praise on the defender.
"My first impression was that this was the biggest man of his generation," Vannuchi said.
"The difference between him and the other players was massive.
"When he took the ball and ran into midfield, no one could stop him. He was like a monster compared to the others. When he played with St-Etienne it looked normal for him, even though he was so young."
Vannuchi also compared Saliba to world class centre back talents Raphael Varane and Virgil van Dijk, saying he combines the best elements of both.
"A mix of the two styles," Vannuchi explained.
"With Varane because of his speed and power, and with Van Dijk it is the interceptions, the positioning on the pitch."
Another person doesn't agree with all the praise though, with BT Sports commentator Jonathan Pearce still needing convincing - apparently along with Arteta - after watching Le Classique.
"He's not ready for the Premier League, he makes too many mistakes," Pearce said.
Only time will tell who is right…