The game was just 10 minutes old when Mane's low cross evaded both Arsenal centre-halves to allow Firmino to take a touch and fire high into the net for his first goal in seven matches but third in four league matches against the north Londoners.
Arsenal lost to Liverpool 3-1 Saturday at Anfield, the first time it has been defeated by Liverpool twice in a season in 17 years. Sanchez was introduced at half-time and made an immediate impact, creating chances and providing the assist for Danny Welbeck's goal.
Yet even as Anfield grew increasingly nervous in a much more even affair, Wijnaldum ended the home fans' worries by converting an injury-time strike.
A week after winning the League Cup for United with a double against Southampton at Wembley Stadium, Ibrahimovic endured a frustrating return to league action by seeing his 72nd-minute penalty clawed away by Artur Boruc. Wenger admitted his mistake and accepted responsibility afterward. Okay, Liverpool allowed them to play to their strengths but it was a superb display from Jamie Vardy and Co in their first game since the sacking of Claudio Ranieri. If they are going to bring in players go and do it early and get them ready for pre-season. That can be attributed to two factors: poor defending from the midfield back, and the inexplicable decision to rest Alexis Sanchez until the second half.
In the subsequent fracas, Bournemouth's Andrew Surman pushed Ibrahimovic over and was sent off for drawing his second yellow card. "My intention was not to injure him but to protect myself", he said.
Georginio Wijnaldum scored the victor in stoppage time to seal all three points for Liverpool from a beautifully executed counter attack.
"Who can I blame?"
Liverpool rebound from their recent thrashing by Leicester with a convincing 3-1 victory of their own over Arsenal. It was the Foxes' second straight win since Claudio Ranieri was sacked.
Sanchez's second-half introduction immediately changed the dynamics of the match, and it was the Chilean's through pass that found Welbeck in the box to get the Londoners a goal back.
"We need to make the right transfers", Klopp said.
This season's vitriol towards the long-serving Wenger has been noticeably more spiked than usual - a failed title challenge and European humiliation at the hands of Bayern Munich have seen calls for his departure grow ever-louder.