The Reds seemed to be heading for a tenth defeat in 11 league outings courtesy of Chris Basham's first half strike.
However, Conor Hourihane, after missing an earlier penalty, fired in a 94th minute equaliser to ensure the derby clash ended level.
Johnson said: "That was a fantastic finish, a great strike. If you want that to fall to anybody in that area on his left foot, it was Conor.
"It meant a lot to him, you could see by his celebration. The keeper saved the penalty and he was hurting from that.
"But he didn't hide, and when he needed to step up he did - a great strike and in my opinion, thoroughly deserved because second half we hit the bar, hit the post and missed the penalty.
"It could be a big point for us. It's a young group, but when you hear the comments they're coming out with you think: OK, they're starting to mature a bit now.
"A lot of the stuff (they are saying) is positive and about going on a run and it was nice to hear.
“It could be a big goal for us, it's proof. We had a nice embrace after because he realised it was an important goal for us all and for the team, because the team deserve it.
“They have been working very hard in training. They are good lads. We are a bit naive at times but we know that, and Conor's one that's taken it on, become a leader."
Johnson’s sense of jubilation at rescuing a point was in contrast to that of Nigel Adkins, whose side are now without a win in six league outings.
“I had been looking for a response and we did that,” said Adkins, whose side lost 4-2 at home to Shrewsbury Town in midweek.
“There was plenty of passion from my players. We got a good goal, could have scored a few more and i thought the Barnsley goalkeeper was outstanding.
“Saying that, George Long made a very good penalty save for ourselves. “We conceded at the end. It was a fantastic strike.”