Rangers saw their lead wiped out having gone ahead through Dan Shittu's first-half goal and Holloway claimed they must now win six of their last seven games to make the play-offs.
He said: "I'm not a happy man. The players talked about concentration - I
talked about desire.
"If you've got the desire, you make sure you drive other people on to where they should be. That didn't happen.
"We had some great chances from set-pieces but some players lacked that bit of nastiness to get in there and get their heads on it.
"In the second half they came at us like a red and white swarm and showed unbelievable desire."
But Holloway insisted Rangers still have a realistic chance of finishing in the top six.
"It will be that bit harder after today, but we can still do it," he added.
"We're on the rails and are a bit boxed in after today. We need to find an opening, wriggle through the gap and then run like the clappers to the line."