But Rovers stormed back in the second half and David Dunn equalised with 18 minutes remaining as the German stopper allowed a speculative effort from just outside the penalty area to elude him.
Blackburn ended the game with ten men when Ryan Nelsen was dismissed for a second bookable offence but boss Mark Hughes was satisfied with the point which continues his sides unbeaten start to the campaign.
"I thought we were absolutely brilliant today.
"I thought we totally dominated the opposition from start to finish.
"I thought we were hungry for the ball, we played the better football, really put some pressure on them and they weren't allowed to play their normal game.
"I just thought we were excellent and played the best football and created more chances, but in the end when you lose a man you have to be happy with a point."
It was David Dunn's strike that led to Lehmann's gaffe and Hughes joked that it should go down as an own goal before praising the midfielder, who is now enjoying his second stint with the club.
Hughes added: "I told him it was an own goal but he wasn't too happy with that, but I think he's claiming it and rightly so.
"I thought David Dunn was absolutely immense today, we had a different game plan, they have good individual talent with the likes of Fabregas in midfield so we wanted to nullify their affect and I think we did that."