Wijnaldum replaced the injured Andrew Robertson at half-time and added to an early goal from Divock Origi to level the aggregate score at 3-3. Origi then scored his second of the game to put Liverpool ahead in the tie and into the Champions League final for the second straight year.
"I was really annoyed at the manager for putting me on the bench!"— Football on BT Sport (@btsportfootball) May 7, 2019
Nobody puts Gini in the corner.
Wijnaldum came on with a point to prove pic.twitter.com/Rvm7gv2hgA
"It's unbelievable," Wijanaldum told BT Sport at the final whistle.
"After the game in Spain we were confident that we could score four at home and win 4-0. I think the people from outside doubted us and thought that we couldn't do it, but once again we showed that anything is possible," he added.
"[I'm] really emotional, because I was really angry at the manager that he put on the bench. I had to do something and when I came on I just tried to help the team. I'm happy I could help the team with two goals and overall it was a good team performance."
Wijnaldum's impact after coming off the bench of the second half cannot be understated.
2 - Georginio Wijnaldum is the first substitute to score twice in a Champions League match for Liverpool since Ryan Babel against Besiktas in 2007. He's also the first ever sub to score twice against Barcelona in the competition. Genie. #LIVBAR— OptaJoe (@OptaJoe) May 7, 2019
Opta stats have revealed that he is the first Liverpool substitute to score twice in a Champions League game since Ryan Babel managed a brace against Besiktas way back in 2007 - and that was two late strikes in an 8-0 group stage win, not the semi-final second leg.
Wijnaldum is also the first ever substitute to score twice against Barcelona in the competition.
The Dutchman and his teammates must now wait until Wednesday night to learn the identity of the team they will be facing in Madrid when Tottenham and Ajax meet in Amsterdam.
Liverpool must also bring themselves back to earth and prepare for Sunday's Premier League clash against Wolves, with the title still up for grabs if Manchester City fail to beat Brighton.