But the hosts suddenly came alive and, unbelievably, they were ahead by the 58th minute with goals from Alexis Sanchez, Granit Xhaka and Mesut Ozil turning the game upside down.
Jack Wilshere says he "definitely" wants to stay at Arsenal and hopes a new deal can be agreed soon.
"So we gave them [a chance], we opened the door for them in these five minutes and they, with all respect, took the chances".
"We are on our way and we have to keep the team together and improve", he said.
Firmino made sure Liverpool returned north with a point with a 71st minute equaliser but Juergen Klopp was left scratching his head at how his side squandered two points.
"To avoid mistakes completely is impossible - you to have learn from them", said Klopp having refused to comment on a fresh move for Southampton's Virgil van Dijk during next month's transfer window. They all have a lot of pace. "We are a very good football team".
Jordan Henderson will miss Liverpool's game with Swansea City on Tuesday because of a suspected hamstring injury. The captain was replaced by James Milner who, like his manager, believes Liverpool's squad is young enough to improve. "The draw feels really not good, but that's good because we should have won like in all the other draws we have". We couldn't do it so it's a bit bittersweet, with being in front but then drawing the game.