Charles N'Zogbia handed Villa the lead 10 minutes after half-time only for the midfielder to put through his own net as the hosts' defensive frailties saw their run without a clean sheet extended to 21 outings.
The result left Villa in 16th place, three points above the drop zone with just five games of the season remaining.
"I thought we lost an equaliser through a bad bit of luck after Fabian tried his utmost to go and do the right thing, so you can never criticise that," Lambert told Sky Sports.
"He is okay and his performances of late have been excellent and the lad has tried to head it away, which, as I said, you can never criticise anybody for trying the right thing.
"But he's a young guy who has had a really difficult time with injury, but playing ever so well for us at this time."
The Scot was pleased with his side's overall display and felt the point was the least his side deserved.
"I thought we were very good," he said. "We had a lot of the ball and with the chances we had, I thought we were a threat the whole game and I thought we lost an equaliser due to a bad piece of luck."