Man-of-the-match Bowyer scored what proved to be the winning goal 16 minutes into the game against Roy Hodgson's side at St Andrews on Saturday afternoon.
"When Lee first came here I had some people raising their eyebrows saying his legs had gone and that he was not the same player that he once was," the Blues boss said after the match.
"He has proved a lot of people wrong. He can run all day, has class about him, and is a real leader.
"The goal was the one bit of class we produced in the game. It was trademark Lee Bowyer.
"It was a late run onto a great pass and the execution was world-class."
McLeish also praised the character and resilience of the team as they withstood some extensive late pressure from the visitors to hold onto their slendour lead.
"We played a tough game today that was sometimes not too pretty from our point of view," the Blues boss added.
"We've played better than that and lost games but winning games is sometimes not about playing pretty football.
"Today we showed that you can win a football match with steel, determination and resilience.
"There's no getting away from the character I have in my dressing room."