Liverpool FC were trailing 3-0 from the first leg at Camp Nou following goals from Lionel Messi and Luis Suarez.
The home side were without their attackers Mohamed Salah and Roberto Firmino for the return fixture on Merseyside.
Divock Origi was drafted into the Liverpool FC side and the Belgium international required a mere seven minutes to make the breakthrough for the Premier League side.
Sadio Mane won the ball on the edge of the area before Jordan Henderson evaded Gerard Pique to force a save from Marc-Andre ter Stegen, but Origi pounced on the rebound.
Liverpool FC were forced to make an early change at half-time when Georginio Wijnaldum replaced Andy Robertson.
The Dutch midfielder scored twice in two minutes when he finished with a low strike before a well-placed header.
Liverpool FC striker Origi scored his second of the night with a brilliant finish after quick thinking from Trent Alexander-Arnold to take a corner with the FC Barcelona defence unprepared.
And former Reds captain McManaman was full of praise for Origi after his clinical finish.
“It’s an incredible finish from the big man,” McManaman told BT Sport.
“It was about staying alive and staying alert. His first was easy. His second was difficult. How he put it away.”
Liverpool FC will take on Wolverhampton Wanderers in their final fixture of the Premier League season at Anfield on Sunday afternoon.
The Reds are in second place and a point behind defending Premier League champions Manchester City, who will face Brighton.
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