Nigel Pearson has lamented his side's ability to defend set-pieces as Bristol City left Kenilworth Road empty-handed.
The Robins dominated possession and arguably had the better chances but were undone by two crosses on either side of half-time.
Despite starting the brighter of the two sides, City fell behind when ex-Rovers defender Tom Lockyer headed home James Bree's corner five minutes before the end of the first half.
Andi Weimann scored a deserved equaliser before City's fragile defence was exposed for a second time when they failed to deal with Bree's delivery after Cam Pring had conceded a free-kick.
Elijah Adebayo took advantage after the visitors were unable to clear their lines and he poked home from close range past a helpless Max O'Leary.
"We can't defend set-plays at the moment, we're relying on one, two or three players winning everything and if they can't then we don't have a collective response or we haven't been able to find the collective response we need and that's a frustration," Pearson said.
"We've had it too often, we've not shown ways of being able to get results in tight games when the least we should have got tonight was a point. It's a missed opportunity for us, it's happened too often this season and it remains a big frustration for us.
"We created the best chances in the whole game, I don't remember too many attempts on goal or saves that Max had to make. It's a missed opportunity. There are positives but I'm not going to get into talking about them, it was a frustrating night for us."
For all City's dominance in the first period, they had to wait until the 55th minute to register their first shot on target.
A minute later, captain for the night Weimann scored his 14th of the season when he brilliantly found the bottom corner after being picked out by Antoine Semenyo.
The Austrian would later squander two more opportunities and Pearson admitted he can't rely on his forwards bailing out his defenders every game.
"There were lots of good aspects but unfortunately it's another game where we've come away with nothing because we were not efficient enough," Pearson added.
"When the pressures on the forwards to take chances and nick a point, we should be in a better position than that. We can't expect to be in a position to score two goals every game to get a point."
When quizzed on the reasoning behind Semenyo's substitution for Nahki Wells on 75 minutes with City chasing an equaliser, Pearson responded: "Semenyo was booked, he made two later challenges and we can't put a risk on him."
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