Jim Magilton said too many players were below their best as Blues went down at Doncaster.
A first-half header from Shelton Martis gave the Yorkshire club the points with the Town boss saying: "We didn't show enough quality to win the game.
"We had chances and could certainly have got something out of the 90 minutes but overall four or five players didn't 'turn up' for us.
"Doncaster passed the ball well and deserve a lot of credit and we were nowhere near the level we have shown recently.
"Darren Ambrose did well when he came on, made their 'keeper make a top class save and he will get better with games."
Jim refused to use the unsettling build up to the game surrounding David Norris as a possible reason for Blues' disappointing display.
"It wasn't a factor at all. We are not using that as an excuse. We simply didn't have enough quality performances," he added.