The hosts have struggled to translate their domestic form into European success this term - while they sit top of the Primeira Liga with 28 points from a possible 33, they came into this encounter having lost each of their opening four matches in Group D to suffer an early elimination from the tournament.
However, despite coming up against leaders and already-qualified Inter, who were unbeaten across their own four continental clashes prior to kick-off, Benfica were dominant throughout the opening period.
They needed less than five minutes to move in front, as Mario swept home Casper Tengstedt’s clever knockdown on the latter’s first Champions League start.
Mario spent five years on the Nerazzurri’s books between 2016 and 2021 but struggled to consistently produce his best.
He was at the top of his game in Lisbon though, and he soon had a second, finding the bottom corner again after a combination of Tengstedt and Rafa Silva dispossessed Kristjan Asllani on the edge of his own box.
Inter were shell-shocked, and other than a Marko Arnautovic effort that was well-saved by Anatoliy Trubin, they offered next to nothing offensively.
That was in stark contrast to their opponents, who extended their advantage further shortly after the hour-mark when Mario bundled Tengstedt’s wonderfully weighted ball over the line to complete his treble.
Inter could hardly be worse after the break, but their resurgent start to the second half still came out of nowhere. Carlos Augusto and Alexis Sanchez both had efforts saved by Trubin early on before the Chile international’s corner was headed towards the back post by Yann Bisseck, allowing Arnautovic to apply the finishing touch from close range.
They were just one goal behind with less than 60 minutes on the clock too, when Davide Frattesi spectacularly volleyed Francesco Acerbi’s cross beyond Trubin’s desperate dive.
Simone Inzaghi’s men now had the bit between their teeth, and although their quest for an equaliser left them open at the back, they restored parity soon after.
Marcus Thuram was fouled in the penalty area by Nicolas Otamendi, compelling referee Andris Treimanis to point to the spot. Sanchez is no stranger to spot-kicks, and he kept his cool from 12 yards, sending Trubin the wrong way.
The rest of the game was end-to-end as both sides went in search of a winner, with Emil Audero’s marvellous stop to tip Angel Di Maria’s shot over the bar the pick of the late opportunities before the Portuguese side were reduced to 10 men following António Silva’s wild lunge on Nicolo Barella.
In the end though, the two outfits had to settle for a share of the spoils which does little to help their respective causes - Inter remain second behind Real Sociedad, while Benfica must now beat Salzburg on Matchday six by more than two goals to earn a spot in the UEFA Europa League play-off round.
Flashscore Man of the Match: Joao Mario (Benfica)
Read all about the dramatic Inter comeback here.
Real Sociedad fail to break down Salzburg in drab draw
In the other game in Group D, Real Sociedad failed to capitalise on the chance given to them by Inter's dropped points to move two points clear at the top.
Salzburg held firm despite the Spanish side dominating possession as the game finished 0-0.
Read more about the match stats here.
