There was some debate over whether the much-maligned midfielder deserved to come back in to a team that had demolished Inverness 6-0 in midweek.
But, the former Hibs player repaid his manager's faith in him after only five minutes by grabbing the opener with a wonderful volley -Glenn Loovens added a second after the break.
"Are you surprised?" smiled Lennon when asked about Brown's performance.
"He's got his detractors but we all know what he can do.
"It was a wonderful performance, he led the team brilliantly with good energy and quality and it was a wonderful goal he scored as well.
"If we hadn't had him we might have struggled.
"We had a decision to make for this game. Ki Sung-yueng's performance against Inverness was at a very high level but we feel that Brown can be at his best in games like this.
"I've said before, he has been a big player for me and it showed today, I thought he was fantastic."
Lennon claimed his side made heavy weather of a victory that should have been more comfortable.
"At 2-0 up we should have been coasting," he said.
"The goal we gave away was criminal from our point of view. The one player that can change a game in their team is Riordan.
"The game went flat at times and some individuals were not at their best but when you go 2-0 up you should see it out comfortably.
"When it goes to 2-1 it gets a bit edgy but we had enough chances to see the game off.
"It didn't help that we lost Charlie Mulgrew at half time to a hamstring injury.
"We had to reshuffle a bit but we brought the problems on ourselves really by not doing the basics well enough.
"But it was important that we won the game and put the onus back on Rangers and we did that."
Lennon will have a look on television at the incident which saw his striker Anthony Stokes booked for diving in the Hibs box.
He said: "We haven't spoken about it yet and I didn't get a good view but if he has we don't condone it if he has done it.
"We will have a look at it again."