Sean O'Driscoll has urged his Doncaster side to be more ruthless after neighbours Barnsley snatched a 1-0 away win.
Rovers were the better side for much of the South Yorkshire derby but Adam Hammill fired a classy 74th-minute winner to give the Tykes local bragging rights.
That secured a third straight victory for Barnsley, who continued their climb away from the foot of the table since the appointment of Mark Robins.
But O'Driscoll fears Doncaster could slip into the drop zone if they do not become more clinical in front of goal as a seventh game without a win leaves them just three points above the bottom three.
"Getting beaten when you have outplayed the opposition is something of a common theme for us," he said.
"We made one mistake and that's enough at this level. We've been here before, but I would take that performance every day.
"If we perform like that every week I will have no complaints, but I am disappointed with the result. If you don't take your chances you give the opposition a chance.
"We don't score goals. Any man in the street can tell you that. To score you need to create chances and we do. We have most of the attributes - we are just missing that little bit at the end."
Doncaster have now scored just 11 goals in 12 league games yet it was O'Driscoll's defence that looked shaky early on.
Hammill's weak shot had Rovers goalkeeper Neil Sullivan scrambling across his line before Emil Hallfredsson went close with a header.
The hosts replied with James Hayter poking wide from five yards from James Chambers' pull-back while Billy Sharp had a goal disallowed for offside.
James Coppinger then went close, with his flicked header forcing an acrobatic save from Luke Steele.
Doncaster remained on top after the break as Dean Shiels curled a shot against the bar before Martin Woods drove a free-kick just wide.
But the Tykes took all three points as Iain Hume's corner found Hammill at the near post and the winger was given space to turn and blast a shot across Sullivan into the far corner.
"We were under the cosh for a lot of the game but we kept our shape and that's important," said Barnsley boss Robins.
"It was very similar to the Swansea game. You have to keep your discipline - that is what we have done and we got a good goal on the back of it.
"Once we got the goal we improved a lot. I think there was a bit of anxiety in our play and that was apparent until we scored and then we got a lift and some confidence.
"From my perspective that's a magnificent three points," he added. "It gets us nearer the middle of the pack.
"This is a tight league and a win like that has a big effect. I am extremely happy but we have another tough game coming up against Nottingham Forest."