Despite making a slow start to his fourth season on Merseyside, the Brazilian rediscovered his finest form with a hat-trick against the Gunners and became the toast of supporters on Twitter.
Firmino opened the scoring for Liverpool with his latest no-look finish, doubled the advantage with a superb solo effort and completed the treble from the penalty spot.
Jurgen Klopp was incredibly complimentary of Firmino and the performance in general, noting: "We knew in the second half that the game wasn't finished, so we wanted to control it.
"Mo Salah gave the penalty to Bobby [Firmino] and I almost cried because we all know how much Mo wants to score goals. It was really nice. Christmas is over but not between the boys!
Praise for Firmino in England
"The response [to going behind] was world class. We stayed calm and really forced the mistakes. Firmino's second when Sadio [Mane] won the ball - wow. It was perfect defending."
There was so much to be pleased about with Liverpool's performance and naturally, Firmino became one of the most discussed topics on Twitter throughout the evening.
However, that wasn't completely reserved to England as Firmino was making headlines in his native country, according to ESPN Brazil.
Reaction to Firmino back in Brazil
It's been well-documented that Firmino doesn't get the credit he deserves back in Brazil and Liverpool fans have often been bemused that Gabriel Jesus is so regularly selected in his place.
Even Brazilian fans themselves have been somewhat dismissive of Firmino in the past.
That certainly was the case after his Arsenal performance, though, with Jesus becoming a trending topic on Brazilian Twitter and it wasn't for complimentary reasons.
A number of fan comments, after Liverpool 5-1 Arsenal, roughly translated to: "And I had to put up with Gabriel Jesus, who couldn't dominate a ball at the World Cup."
"Someone give me the scientific explanation for this guy being reserve to Gabriel Jesus in the World Cup, please," another supporter added.
Brazilian commentator Mauro Cezar Pereira even remarked during the game: "I am obliged to remember that the Firmino in the World Cup did not play. He was on the bench, he was coming in during the games."
At long last, it seems Firmino is getting the credit he deserves.
Jesus has endured a difficult start to the season and after Firmino bagged a hat-trick against Arsenal, even the biggest skeptics are beginning to favour the Liverpool man.
Whether or not Tite follows this school of thought or not remains to be seen but there can be little doubting that Firmino holds the upper hand right now.
Firmino is one of the most unique number nines in the world and on current form, the Brazilian fans should have their wishes answered. Besides, it certainly deserves it.
Do you think Firmino deserves to start for Brazil? Have your say in the comments section below.