The prop endured a difficult first half where he twice conceded penalties in the scrum during the tourists' 16-15 defeat to the Wallabies in Melbourne.
Despite the defeat, Youngs insists that Vunipola deserves credit for turning his own personal performance around.
"It was good that we turned it around," Youngs told Sky Sports News. "A few decisions didn't go our way. Credit to Mako, he stuck with it. We changed a few things around and got on top with it.
"You have to talk to him, say 'get rid of it'. It's like me with a bad lineout throw - if you have one you have to get on with it. Luckily, we got the right thing in the end. They just caught us a few times. As soon as you lose the hit you are under pressure straightaway. There is a lot of weight going to come through that way. But we got it sorted out and improved.
"He (referee Craig Joubert) wanted Mako to go closer. He didn't want anyone to go on the floor. You have to adjust to it. Every referee has his way of reffing it. We do a lot of review on it. You can have all that, but when you get on the pitch it can go either way and you have to adjust as quickly as possible, which isn't always easy."
The series is currently level at 1-1.