The 5.20pm kick-off time at The Keepmoat Stadium meant that Blues knew that should they take maximum points from the match against Rovers then they could extend their lead over Reading to seven points following the Royals 1-0 home defeat by Ipswich earlier in the day.
Blues duly obliged and two first half goals from Cameron Jerome and Hameur Bouazza earned them maximum points with a 2-0 win against an in-form Rovers side.
"I think at last we took advantage of one of our rivals (Reading) slipping-up," McLeish told Sky Sports after the match.
"It was another opportunity and this time we've taken it .
"We've passed up a few and I think that has frustrated the Birmingham fans and us if the truth be told.
"But today was a real professional performance with some good finishing.
"I thought we were comfortable winners."