#3 Neymar's single-mindedness has mixed results
Without running mate Kylian Mbappe for company in the final third, PSG star Neymar felt compelled to again be the matchwinner, just like he was against Dortmund five months ago. Three minutes in, he could and should have broken the deadlock.
Icardi's timely interception in transition saw the ball break free for him on the counter, with only the goalkeeper to beat. He ultimately skewed his effort well wide of the far post and judging by the bench's reaction, they knew how much he should have scored too.
PSG head coach Thomas Tuchel cut an exasperated figure pitchside after another promising move broke down as Neymar's purposeful run forward was ultimately followed by the ball trickling harmlessly wide of Marco Sportiello's far post.
Icardi's movement was both baffling and didn't provide the Brazilian with an option in the box to really aim for, but the latter still should have improvised better than he did.
Naturally, he proved what he can do with the ball at his feet in full flow just before the half-hour mark. He effortlessly skipped past goalscorer Pasalic, before proceeding to slalom his way towards Atalanta's area and fire narrowly wide from distance.
The commentators continued to bemoan Neymar's lack of help in Mbappe's absence, as Sarabia and Icardi didn't exactly exude confidence and were making defending fairly routine for a determined Atalanta backline - protecting a lead by this stage.
So when Mbappe did finally come on, things changed for the better and Neymar suddenly found himself with a reliable partner to dovetail with. His wasteful finishing continued and the decision-making remained frustrating at times.
However, the pair combined to create Choupo-Moting's winner and Neymar created his third Champions League assist of the campaign for Marquinhos' equaliser just beforehand.
With 16 successful dribbles, five key passes and 25 duels won - as well as a whopping nine fouls suffered - those final few minutes were a perfect representation of Neymar turning perception upside down after a divisive evening.
#2 Atalanta found themselves deservedly ahead
PSG goalkeeper Keylor Navas was busier than he would have liked to be in the first half, making important saves to tip away Hans Hateboer's header before thwarting Mattia Caldara's goalward effort from creeping into the bottom corner.
Although the latter was ruled a marginal offside, the former Real Madrid man wouldn't have known and he rightly shouted at his sleepy backline to wake up.
They didn't heed his passionate warning and instead, Atalanta were growing in confidence - Hateboer was the first to every ball while captain Gomez relished getting on the ball wherever possible to create an opportunity.
So, when Pasalic broke the deadlock, the finish didn't come as much of a surprise.
Kimpembe's attempted interception on Duvan Zapata inadvertently teed up the former Chelsea midfielder, who curled his strike towards the top corner and away from Navas' despairing dive.
Not content with their one-goal cushion, Atalanta still had chances to add to their lead - while doing their utmost to frustrate Neymar, taking it in turns with persistent fouls.
Albanian centre-back Berat Djimsiti came close on two separate occasions, one in each half, before being replaced on the hour mark for José Luis Palomino.
Gomez seemed to be struggling with a knock and was replaced by midfielder Ruslan Malinovskyi as Gian Piero Gasperini made a double substitution.
However, Tuchel's Mbappe admission was proven true and the World Cup winner's presence off the bench went a long way in helping PSG intensify their pressure late on.
#1 PSG pressure proves pivotal in booking semi-final place with a dramatic finish
Just like the last-16 first leg against Borussia Dortmund, PSG only had themselves to blame for being behind in a fixture of such magnitude.
Even with a depleted starting eleven, it felt like Neymar against the world at times and that's usually not a good omen when he can be frustrated so easily.
Atalanta's backline were more than happy with their attempts to marshal him, forcing the Brazilian into deeper areas and doubling up when he had possession.
Sarabia and Icardi were both quite ineffective, so Mbappe's introduction prompted a different sort of dilemma for the Italians to ponder.
Armed with flashy flicks, intelligent movement and a blistering turn of pace - despite not being 100% - Mbappe stretched the game while PSG continued to probe for an equaliser.
Tuchel made a double substitution as PSG's Gueye-Herrera holding midfield axis were replaced by more creative playmakers in Julian Draxler and Leandro Paredes.
The latter's first meaningful contribution was an outside-of-the-boot pass which teed up Mbappe in transition down the left-hand side. Although Sportiello was equal to the strike, this proved a step in the right direction as far as PSG's creative outlets were concerned.
Neymar continued to threaten as usual but crucially, his decision-making and ability to strike cleanly had evaded him. Time ticked down and frustrations grew as Icardi was replaced by Eric Maxim Choupo-Moting, and Palomino made a goal-saving tackle to partially block Mbappe's promising one-on-one effort.
Choupo-Moting, Draxler and Neymar all had chances flash wide before questions over PSG's mental toughness intensified as the match ticked towards the 90-minute mark.
Although neither provided the finishing touch, the Neymar-Mbappe combination play was key in the final third as Atalanta's hearts were broken by unlikely heroes late on.
The PSG pair created assists for Marquinhos and Choupo-Moting respectively, to fight another day in an unpredictable Champions League campaign.