With injuries limiting his options in recent weeks, O'Neill has turned to 22-year-old compatriot McClean, and has been richly rewarded.
The Ulsterman said: "I couldn't be more pleased with him. He has come in and he has been exceptional.
"He came on in the game when perhaps maybe we seemed to be chasing lost causes against Blackburn and lit the place up.
"His emergence has been fantastic."