The visitors offered a sign of their intent early on, with Daniel Podence testing Wojciech Szczęsny inside 20 seconds, but it still didn’t take long for Barra to start flying forward.
After Marcus Rashford had already sent an improvised attempt over the crossbar, Fermin offloaded the ball to Lamine Yamal and took it back before hitting a shot that went in despite two Olympiacos defenders getting a boot to it.
Rashford came close again shortly after, smashing his free kick into the side netting, though it wasn’t all one-way traffic, as Szczesny was given a scare when Dani Garcia’s shot took a deflection off Marc Casado before eventually settling on the roof of the net.
Having seen some unexpected vulnerability amongst the opposing backline, Olympiacos ventured forward again, with Gelson Martins seeing his shot blocked by Jules Kounde and Lorenzo Pirola heading over the crossbar.
But they suffered a blow just before the half-hour mark, with Chiquinho being forced off through injury – and it’s disruptive nature may well have played a role in Barcelona’s second, as Kounde then glanced a header agonisingly wide before Fermin punished a sloppy moment from the visitors in the 39th minute, collecting Dro Fernandez’s pass and finishing to double his and Barca’s tally for the evening.
Fermin was denied a third shortly after the restart when Konstantinos Tzolakis palmed his glanced header away.
Ayoub El Kaabi then saw his header ruled out due to Podence being offside, but Eric Garcia had handled the ball, and the striker recomposed himself to fire his resulting penalty in off the post.
Once again, this felt like more than a formality for the Spanish champions, but the visitors’ momentum was stunted just three minutes later as Santiago Hezze was shown a second yellow card after being adjudged to have caught Casado, following a similar incident involving Pedri in the first half.
And Olympiacos’ night took another turn for the worse soon after, when a penalty was given for Tzolakis bringing down Rashford, and Lamine Yamal slid his spot kick down the middle.
Barcelona were in no mood to show any mercy as they scored three goals in five minutes to complete the rout. Firstly, Rashford wrongfooted Tzolakis twice for brilliantly taken goals, while Fermin smashed the ball home to complete his hat-trick between those efforts.
That period added gloss to the scoreline, as the Blaugrana emphatically responded to their defeat against Paris Saint-Germain to make it two wins from three UCL contests this term. They also leave Olympiacos stuck on one point, with the Greek giants having now lost three of their last four matches across all competitions.
Flashscore Man of the Match: Fermin Lopez (Barcelona)