If Liverpool's spluttering forwards end up remembering this as the day when their luck turned then they will owe a big debt of gratitude to Yehor Yarmolyuk. This was a game with a very clear before and after.
Andoni Iraola will hope surviving one of the toughest tests the Premier League has to offer is a sign his methods are starting to work, but Liverpool's manager will not forget it was a very different contest after Yarmolyuk's red card for a butt on Jérémy Jacquet left Brentford trying to defend a 1-0 lead with 10 men for the entire second half.
Brentford, who later lost Vitaly Janelt to a second yellow card, could not hold out. They raged at John Brooks's officiating after their unbeaten start ended, but they had only themselves to blame after tumbling out of the top four. Brentford pressed the self-destruct button when they had Liverpool on the ropes. Yarmolyuk was never going to get away it in the video assistant referee era and Liverpool made the midfielder pay.
Iraola was delighted with how an attack worth close to £400m made the numerical advantage count after half-time. Most important was a telling contribution from Florian Wirtz. The £100m signing has struggled with the responsibility of playing as Liverpool's No 10 since joining from Bayer Leverkusen, but this time he was decisive. The clever pass to release Victor Muñoz for a sharp equaliser was his second assist of the season and was followed by Bradley Barcola creating a goal for the first time since his move for an initial £106m from Paris Saint-Germain, the French winger's header teeing up Alexander Isak to complete the turnaround in the 70th minute and lift Liverpool into fifth place.
The challenge is to push on. Isak's Liverpool career has been stop-start since his £125m move from Newcastle, injuries holding the forward back. The Spaniard was critical of some sloppy finishing from Barcola, but was readier to dish out the praise for Wirtz's intelligence in tight spaces in the second half. It feels significant that both of Wirtz's assists have come for Muñoz.
"A good battle today," Iraola said before switching focus to Barcola and Wirtz. "Both had a lot of influence. Bradley and Flo, they are players that against 10 men are lovely to have."
There was not much between the sides before Yarmolyuk's rush of blood to the head. Isak returned after missing last week's defeat to Manchester City and Liverpool shaded the early openings. Barcola almost punished an error from Janelt, only to miss a chance to build on his midweek hat-trick against LASK. Isak nodded over from a good position.
Brentford responded with a series of fast breaks and Liverpool had to be strong. They looked readier for the threat posed by Brentford than when they folded in this fixture under Arne Slot 12 months ago. Jacquet, quietly impressive in central defence, made a crucial tackle to deny Igor Thiago. The initial problem for Liverpool was more their expensive attack was yet to gel.
Michael Kayode was keeping Barcola in check and Keane Lewis-Potter was edging his battle with Muñoz. Wirtz was timid and Liverpool's worries grew when they lost Dominik Szoboszlai to injury.
With Ryan Gravenberch suspended, Liverpool were light on midfield options. Trey Nyoni replaced Szoboszali and the 19-year-old's introduction was followed by a whirlwind spell. Iraola was unhappy when Liverpool had a penalty overturned as replays showed Dango Outtara got a clear touch on the ball before colliding with Alexis Mac Allister.
Brentford were pumped up after the VAR intervention and soon made Liverpool rue a failure to clear their lines. The ball came back too easily, Mac Allister backed off Thiago, who crossed for Lewis-Potter to run in from left-back and head into the top corner.
"We were edging it," Keith Andrews said. Brentford's manager wants his team "to play on the edge", but felt too many decisions went Liverpool's way. However, he had no complaints about the first red. He said Liverpool were "cute and clever" during the incident, but promised that Yarmolyuk would learn from his mistake.
They were into six added minutes at the end of the first half when the midfielder clashed with Jacquet before a Liverpool corner. It was more of a jut than a proper blow, but it was enough to justify the sending off. Brooks checked the pitchside monitor and his decision was not a surprise.
Liverpool took a while to adjust in the second half. They encountered further complications when injury forced Jeremie Frimpong off seven minutes after replacing Ronald Araújo at right-back. Mac Allister let fly from distance, but Caoimhín Kelleher saved and Rio Ngumoha, on for Frimpong, crossed for Virgil van Dijk to volley wide.
Brentford began to wobble and they were caught on the counterattack in the 62nd minute. Wirtz dropped back and played a clever pass inside Lewis-Potter. Muñoz raced clear, cut back and drilled a low shot into the far corner with his left foot.
The change in mood was dramatic. Barcola sliced a volley just wide, but the winner was coming. Mac Allister took a pass from Wirtz and crossed. Barcola headed down and Isak finished from close range.
Iraola was not happy with Liverpool's play once they led. Brentford threatened an equaliser through Thiago and Liverpool were too rushed. There are flaws to iron out, but this was a positive week for Iraola.