Wijnaldum was left on the bench in the second leg of the Champions League semi-final at Anfield, as Barcelona entered the game with a commanding 3-0 advantage after the first leg.
Divock Origi's early goal gave Liverpool hope but the Reds still entered half-time needing two goals to level the tie.
Wijnaldum entered the game at the break and his quick-fire double in the 54th and 56th minute stunned the visitors to even the semi-final tie at 3-3.
Origi then completed his brace in the 79th minute, completing a sensational comeback and giving Liverpool a 4-0 win on the night and a 4-3 victory on aggregate.
After the game, Wijnaldum revelled in the moment and also confessed that he had a little extra motivation when he entered the game at half-time.
"What can you say, it’s unbelievable,” Wijnaldum told BT Sport. “After the game we were confident we could score four at home and win 4-0.
“The people from outside they doubted us and thought we couldn’t do it, but once again we showed that everything is possible and we won 4-0.
“Yeah, I’m really emotional because I was really angry at the manager that he put me on the bench!
"I had to do something when I came in, I had to help the team… but overall it was a team performance.
“We believed it from the start that we could win 4-0… we knew it was possible.”
Fellow hero Origi also claims the club wanted to fight for the players who couldn’t take part on the night because of knocks.
"It was more about the team [than my goals],” he said to BT Sport. “We did so well. We knew it would be a special night. We wanted to fight for the injured guys. We fought so hard."