Having been comprehensively outplayed, suffering a 4-0 rout in the initial leg of the quarterfinal, Dortmund approached Tuesday's encounter with an unburdened abandon, launching a relentless offensive onslaught against Barcelona from the outset, thereby destabilizing the visiting contingent.

The Barcelona coach, Hansi Flick, drawing upon extensive experience gleaned from numerous encounters and victories against Dortmund during his tenure in the Bundesliga, declared that the fervent home support had led him to anticipate a formidable second leg, notwithstanding his side's four-goal aggregate advantage.

"I harboured a certain prescience that such an eventuality was imminent," Flick confided to broadcaster Amazon Prime. "On this occasion, one is compelled to extend felicitations to Dortmund; they executed a commendably proficient performance. Likewise, commendations are due to my squad, who have secured passage to the semi-finals."

The usually prolific Barcelona forwards Raphinha and Robert Lewandowski, boasting 12 and 11 Champions League goals this season respectively, were conspicuously subdued, their only notable effort a rather meek attempt by Raphinha, easily dealt with by Dortmund custodian Gregor Kobel.

Guirassy, whom coach Niko Kovac lauded as Dortmund's "life insurance" following a match that further underscored his meteoric ascent and positioned him atop the Champions League scoring charts this season, requires merely the commensurate backing of his teammates, a prerequisite for any striker, which he was afforded today.

Dortmund's presumptive elimination from the quarter-final was arguably sealed in the initial leg, further exacerbated by the pre-match confirmation of captain Emre Can and midfielder Carney Chukwuemeka's enforced absence due to injury.

For a time, Guirassy rendered the seemingly unattainable, tangible.

Having squandered opportunities in the initial leg and trifled away a further two early in Tuesday's encounter, Guirassy demonstrated unwavering accuracy from the penalty mark in the eleventh minute following a collision between Barcelona's custodian, Wojciech Szczesny, and Pascal Gross.

Guirassy's decisive header doubled the advantage in the forty-ninth minute, preceding a calamitous own goal by Ramy Bensebaini that severely compounded Dortmund's predicament — Fermín López's low delivery deflecting inadvertently off Bensebaini's ankle — a twofold setback considering the defender's prior instrumental role in instigating the comeback, having provided the assist for Guirassy's preceding strike.

Exploiting Ronald Araujo's defensive misjudgment, Guirassy clinically dispatched a potent strike from proximate range in the 76th minute, thereby notching his hat-trick and ascendancy to the apex of the Champions League scoring charts for the campaign with a remarkable 13 goals.

This result infused Dortmund with renewed optimism for engineering what would have constituted one of the most phenomenal resurgences in Champions League history — a comeback potentially rivaling Barcelona's legendary triumph over Paris Saint-Germain in 2017 — yet Barcelona ultimately withstood the pressure to advance.

Barcelona is poised for a semifinal clash against either Inter Milan or Bayern Munich, marking its inaugural appearance in the Champions League's penultimate stage since the 2018-19 campaign; concurrently, in the other quarter-final encounter on Tuesday, PSG secured passage to the last four with a 5-4 aggregate triumph over Aston Villa, notwithstanding suffering a 3-2 defeat in the return leg.

This setback marked not only Barcelona's inaugural defeat across all competitive fronts since their 2-1 reverse against Atletico Madrid on December 21, but also their premier Champions League loss since September, and a mere seventh blemish in Flick's fifty-match tenure at the helm, notwithstanding the German tactician's unblemished prior record of seven victories in as many encounters against Dortmund during his stewardship of both Barcelona and Bayern.

The hallowed turf of Dortmund's stadium may remain silent to the strains of the Champions League anthem for a considerable duration.

The vanquished finalist in the preceding Champions League campaign languishes eighth in the Bundesliga standings with a mere quinque fixtures remaining, trailing by a sexpartite deficit from the quartette of coveted Champions League qualification berths.