Rovers had umpteen goalscoring chances but had to rely on a late penalty from Tommy Rowe to cancel out Ryan Lowe’s first half header for the hosts.
Crewe snatched a 2-1 victory in the closing stages - and ended Doncaster’s four-game winning sequence - when James Jones fired home.
“It is a disappointing result. We have been on a good run and will have to go on another one now,” said Ferguson.
“It is about winning games and we weren’t ruthless enough, simple as that.
“I am not being critical as the performance overall was a good one. But it is about who scores most goals on a Saturday and they [Crewe] have.
“For whatever reason, we got to 1-1 and lose the game. At Accrington, we got to 2-2 and lose the game.
“It is happening too many times. But when you let people put balls into the box, that is where the danger is.
“We have lost too many late goals and I put that down to concentration.”