Travelling to Portugal with a one-goal deficit, a highly motivated Monaco side offered an early threat at Estadio da Luz, including a nervy moment for the hosts when Breel Embolo had a penalty appeal turned down.
The visitors’ encouraging start was soon forgotten when Wilfried Singo was punished for losing possession just outside the box.
Vangelis Pavlídis took full advantage of Singo’s lapse in concentration, neatly working the space to send the ball across for Kerem Aktürkoğlu to score his fourth European goal of the season and give Benfica a two-goal lead in the tie.
To Monaco’s credit, they showed great character to produce a positive response to Benfica’s opener, with Embolo powering a header against the woodwork just moments before Takumi Minamino found the net to halve the aggregate deficit.
The former Liverpool attacker slotted his near-post shot past Anatoliy Trubin, who would have been bitterly disappointed with his weak attempt to keep it out. With momentum in their favour, Monaco surged out of the blocks in the second period to level the tie within six minutes of the restart.
Eliesse Ben Seghir, who had tested Trubin just four minutes prior, curled the ball past the Benfica goalkeeper after being teed up by Maghnes Akliouche.
Unfortunately for the visitors, they found themselves behind once again when captain Thilo Kehrer clattered the back of Fredrik Aursnes' right leg inside the box, resulting in the award of a penalty after referee Glenn Nyberg had conferred with the VAR.
Benfica’s main marksman Pavlídis stepped up to fire his spot-kick to the left of the unmoved Radosław Majecki, yet the hosts’ joy was short-lived as Monaco fired straight back.
Just five minutes later, super substitute George Ilenikhena made an instant impact, driving a low shot through Trubin’s defences after outmuscling the experienced Nicolás Otamendi within a minute of coming off the bench.
In keeping with the gripping contest, Benfica raced up the other end to provide another dramatic twist, as Orkun Kokcu poked the ball home from Álvaro Carreras’s inch-perfect delivery, sending the home support into raptures as their aggregate lead was restored.
The home side were denied a late penalty by VAR, but it mattered little, as they saw out the final nervy minutes to seal a last-16 tie against either Barcelona or Liverpool.
Flashscore Man of the Match: Vangelis Pavlidis (Benfica)