Sean O'Driscoll insisted Mehdi Nafti's sending-off hindered rather than helped his team as Doncaster dominated 10-man Birmingham but lost 1-0.
Cameron Jerome netted the only goal of the game for Blues, with a well-taken finish from six yards, less than 35 seconds after the restart.
The lively former England Under-21 international pounced on a well-directed flick-on from substitute Marcus Bent to lash home past a stranded Neil Sullivan.
Doncaster started the game very brightly, closing down the hosts and attacking down the flanks.
But Nafti's sending off for a two-footed lunge on James Coppinger after 24 minutes made the St Andrews side more defensive and life more difficult for the visitors.
"Beforehand we were the better team, created more chances and worked hard for it," said O'Driscoll.
"I don't think the sending-off had an effect on the game whatsoever, it just made it a little bit easier for Birmingham to set their stall out and be nice and solid.
"When you lose against 10 men you have to give credit to the opposition - to be fair to them they worked hard but, for me, the sending-off didn't change the game.
"I can't fault the effort of the players. I can't fault what we tried to do.
"We didn't lump it, we played the ball, we created chances and there were one or two penalty shouts we will have to have a look at again on DVD.
"Overall, I thought the performance was excellent. We came here to perform and I think we did," the Rovers boss added.
Birmingham manager Alex McLeish admitted his side failed to really get going but paid tribute to them for picking up all three points against the odds.
"It wasn't pretty but hats off to the 10 men who went out there in the second half, dug deep, rolled their sleeves up and scored a fantastic goal," the Blues boss said.
"I'm grateful for the spirit of the players and I've got belief in them - I know they can play better.
"I think Doncaster passed it well and it was difficult for our midfielders to get close to them.
"But we defended well and had a good, solid back-four display. Maik Taylor also made a phenomenal save."
He added: "It was a sending off, no doubt about it. It was two-footed.
"He (Nafti) looked a wee bit off, he's been out for two weeks now. But you can't go in two-footed, I think Mehdi was a bit tired in that tackle. It was a bad challenge."
McLeish also explained he made peace with Quincy Owusu-Abeyie after the winger stormed off down the tunnel following his first-half substitution.
"We had to explain to Quincy at half-time that you don't go on to the dressing room, you support the team from the dugout and he apologised for that," said McLeish.
"It's fine, we shook hands."