The Egypt international alongside Sadio Mane and Roberto Firmino were excluded from Jurgen Klopp’s starting XI against the Danish Superliga outfit in the Group D showdown.
Without the trio upfront, the Reds laboured to a goalless first-half draw at Anfield Stadium, before the trio was brought on in the second half.
First, it was Diogo Jota who gave Liverpool the lead in the 55th minute thanks to an assist from Trent Alexander-Arnold.
In the 90th minute, Salah, who came in for Takumi Minamino on the hour mark, guaranteed victory for Klopp’s team after netting from the penalty spot – curling the ball past goalkeeper Mikkel Andersen - after he was fouled by Paulinho.
Also, the goal was Liverpool’s 10,001st scored in their history in all competitions, coming 128 years after their first, netted by Jock Smith in September 1892 in the Lancashire League.
As a result, Peter Crouch was in awe of how lethal the Egyptian has been in the final third over the past couple of months.
"Salah's goal record is ridiculous and I feel like he's started the season so sharp. In all his play he just looks unplayable at times. He just looks so on it," he told The Mirror.
"From the moment we kicked off the season you just saw how sharp he was, his passing his movement, it's just all gone up another level. He's incredible.
"We clipped up some of his stuff at BT the other day and I was looking at it, and some of the passes he's making this year, cutting inside, taking two or three players out of the game, setting up attacks...
"Early on when he came and he got his 44 goals [in the 2017/18 season] he was shooting from everywhere, and you felt that the pass was the last resort, but now he's coming inside and looking for people.
"He's gone from being a winger to a ruthless goal machine, and with the potential to set up chances as well. He's a complete player."
They return to English elite division action when they host David Moyes’ West Ham, while Frank Onyeka’s Midtjylland host Nordsjaelland in the Danish Superliga.