An eighth place in the Clydesdale Bank Premier League is their lowest top-flight finish since they were relegated in 1981.
"We can only do so much and when they cross the line they say they are up for it," he said. "Whether or not they are is another matter.
"I felt too many of them were in their shells throughout the season. We need characters and big players.
"Even before I took charge, very rarely did I see any of them go up and knock on the manager's door and ask why they weren't playing.
"You want that, especially when you are going through a bad time.
"When the chips are really down, sometimes the manager shouldn't need to say anything.
"I have a squad of players who in my opinion are as good as anything out with the Old Firm, okay we haven't shown it this season and we need to add quality. But they are just nice boys.
"When something happens in training it is looked upon as a negative.
"It takes everyone aback when they see someone pointing the finger or grabbing someone and saying, 'You are not working hard enough'.
"You need that. If we had more characters like that, they could drag the rest through. Sometimes you need that wee bit of nastiness, in the right way."